It’s mainly a matter of them being jerks at the right time. If it was any other day where the girls weren’t outside they would have never developed to become what they are now. Although oddly enough Applejack always ends up going back to the farm despite not wanting to be a farmer. And Rarity even still helps out with making uniforms for the soldiers. So some of them sort of still found their places in society just a bit differently. I wonder why we never see an alternate version of Twilight?

Oh really, OP? It doesn’t exist because Rainbow Dash performed the sonic rainboom? And I’m afraid it wasn’t just them who were jerks… If you think back to Hurricane Fluttershy, it was shown that most of them found it easy to bully her… So technically they could have just been easily replaced by others at the flight camp… And, in fact, it looks like one bully was missing that day, judging from the flashback in the lost treasure of griffonstone… What would stop him or the others from repeating this scenario if Dumbbell and Hoops didn’t exist or weren’t present at that time?

That would oblige rule #0 .

“only” is the wrong word, equestria exists specifically because of the whole chain of events that happened naturally throughout time. If any one of those events changes, equestria could be in any state, hence the butterfly effect.  
Equestria would have changed if absolutely anything disturbed the natural flow, even Starlights and Twilight’s mere presence in the past disturbed it, but thankfully not enough to cause a noticeable change.  
Even something as miniscule as a pony noticing a unicorn and an unfamiliar Alicorn sitting on a cloud would have resulted in that pony’s future actions being different, and from then on she would cause a ripple as they interact with other ponies, and then you get the ripple of the butterfly effect.  
original timeline:  
pony doing regular daily routine, flying to work, gets to work, converses casually with others, does work stuff, work ends, they go home, do home stuff, sleep. nothing changes, regular timeline ensues, twilight becomes princess, stuff happens, fixes starlights village, goes back in time, splits timeline anyway.  
If twilight and starlight go to past:  
Pony doing regular daily routine, notices unicorn and alicorn sitting on cloud arguing, continue to work. Gets to work, gossips about what they saw, ponies think they’re crazy, mood turns negative, their relationship with others changes for worse, even if only slightly. Doesn’t work as hard, if their work involves other ponies then they probably make everyone elses day just a little bit worse too, resulting in them being a little worse off than they were in the original timeline, that affects their day and everyone they interact with too. Original pony goes home, maybe talks about what they saw with family, family also think they’re crazy. Pony is convinced what they saw was real, gets obsessive over it, gets on other ponies nerves about seeing a unicorn and new alicorn arguing on a cloud, gets sent to psychiatric hospital.  
Fast forward to the future, who knows what’s changed at this point, key events likely still happen regardless so twilight probably still becomes princess eventually. Pony is out of hospital, convinced what she saw was her imagination. suddenly there’s news of an alicorn coronation, it’s the alicorn they saw way back when. Chaos starts all over again, goes to Twilight about seeing her many years ago, Twilight has no idea what pony is on about, this disturbs Twilight’s original flow of time if it wasn’t disturbed already. although Twilight likely still meets starlight again, angers her, maybe catches her, maybe doesn’t, maybe starlight eventually causes the timetravel fiasco again.  
Basically at this point there’s unspeakable chaos, although the influence of that miniscule change really depends on that one pony’s change in interactions, like if she goes home early, she encounters different people at different times or not at all, original encounters never happen and all the behaviours of those ponies are offset as a result, this results in more and more things being different, even if it’s not terribly significant, it all adds up. thankfully there’s some things set in stone if not interfered with, like nightmare moons return, it’s possible that the mane 6 still end up getting together and defeating her, and this can sorta undo some of that timeline chaos, but things will always be at least slightly different, but could still have a huge impact. Like a pony might be standing 1 inch to the left relative to the original timeline, and i’ve seen miniscule differences like that make all the difference in some situations, like in this case a stray magic blast could kill that pony, when in the original timeline it maybe just grazed them.
 
edit: alternatively, since we’ve seen it before, the timeline could be self fulfilling like in that other episode (where twilight goes back in time to tell herself not to worry, causing a closed self-fulfilling loop), meaning they didn’t disturb the timeline at all, but rather followed its “plan” through its linear fashion. Meaning in the regular timeline, for a couple minutes, there was indeed a unicorn and an alicorn from the future arguing on a cloud. In this instance the timeline would be different if they hadnt gone back in time.

You ever have like…
 
Do you have anything you really hate about yourself, and sometimes wish that things would’ve just turned out /differently/ so that the thing you hate never became a part of you?
 
But then you’re also aware that if that hadn’t happened, you really wouldn’t exist as you currently are?

@Antonyourknee  
“You mean, if we hadn’t been jerks to Klutzershy and Rainbow Crash, Equestria would have been destroyed? Dude! We’re heroes! We totally saved everypony!”

@MadVillan  
Because there was something in the present to do so. The map. It specifically sent Rainbow, and lo and behold, Gilda and her became friends again.

@atalarikt  
She may or may not, either way to don’t see the world being destroyed because of it.  
@Starswirl  
They just so happened to meet by coincidence, you won’t be seeing anyone come from the future to repair Gilda and RD’s friendship though.

@Softy  
Celestia totally conspired for that.

Someone should make a fanfic where Fluttershy or Rainbow dash reveals this to Hoops and Dumbbell in the present and see how they react. They deserve to know.

@MadBrony  
they still got their cutie marks did they not?

@Whatevs  
Yes, they would eventually get their marks, but without their friendship bond, Equestria would fall.

Don’t mess with destiny.

@MadVillan  
The magical map inside the crystal castle of the Alicorn Princess of Friendship disagrees.

Just like Bulk and Skull the truest heroes out there.

@MadVillan  
Not really, she may restore Griffonstone one day, and rule it thanks to her friends.

inb4 It’s a Wishful Life

Fate has a strange way of doing things.

@0particle  
Except for Gilda, her friendship doesn’t matter.

I love that.

@Whatevs  
Nah, we all saw the last episodes.

Everyone is important

Nah, the pre-destined nature of the cutie marks means they would have gotten their marks eventually.

thanks dickheads