@orbsah  
I prefer to believe that was their own (read: Twilight’s) magic that pulled that off. That they didn’t win because of directly friendship, but because Twilight nutted up and fought back.
 
And if they don’t need it anymore, well that’s even more reason it didn’t need to come back.  
_{I have to go to work.}

@PonyPon  
At this point Twilight and her friends already surpassed the tree and didn’t need it anymore to blast King Sombra. So, you have kill the Mane Six to accomplish what you want.

@orbsah  
Because its the source of all the fix-everything magic that several ‘save the day’ moments rely on to happen and a few other bad story elements.
 
At its core, it’s God. And the characters we root for don’t need that much help. Or that much Validation.

@PonyPon  
Why?

@orbsah  
Yeah, so?

@PonyPon  
We all know you hate it/her?

The destruction of the Golden Oaks Library was one instance they openly toyed around with the concept of death. Literal DEATH.

Maybe this thing is a reincarnation?

@orbsah  
I think it would make it more exciting for the people who want it alive.
 
For whatever reason.

@PonyPon  
After several episodes we all would assume it as gone forever. It would be weird to see it resurrected again after assuming its death.

@orbsah  
How? the tree still gets to live and the villains don’t look completely outmatched and outgunned.

@Sontersum  
They weren’t really planning to kill it.
 
@PonyPon  
That would be terrible.

@Sontersum  
The loss didn’t even get time to breathe.
 
If there were maybe half a season and some ground stealthily taken by the villains first, i wouldn’t have hated its revival so much.

@orbsah  
Reviving the tree of harmony would lessen the impact of its death, it didn’t stop them from doing it anyways.

Reviving the library would lessen the impact of its death.

Truth. I want the library back.

@Frustration in Excelsis  
Well you said didn’t get a toy but it was a toy however the toy was already publicly known by the time it was in the show

@northern haste  
… yes? Clearly? I just made an adjectival form for the noun.

@Frustration in Excelsis  

 
You mean rainbow power?

@northern haste  
You’d be genuinely surprised how many “obviously toyetic” things there have been that never got toys – like the Rainbow Powered mane six, or the changedlings. None of that was ever really used as toy material.
 
Meanwhile, a lot of the toyline characters and concepts – like several different alicorn princesses – have no presence in the show.
 
We joke about this being a twenty two-minute toy commercial, but there’s a much bigger disconnect between the show and the toys than a lot of people assume.

@Ihhh  
Because you asked.

@PonyPon  

 
By who? I assumed that people disliked out for other reasons.
 

 
What about the crystal empire? Since when did people complain about it’s design?
 

 
No it doesn’t. It uses much lighter blues and far less purple. It also doesn’t feature crystals, and I’ve never heard anyone complain about it.
 

 
Then why even bring it up?

@Ihhh  
The crystal motif was thought to be overdone since Twilight’s castle first appeared.
 
And that was after the crystal empire.
 
Hell, even the new Canterlot throne room uses a far-too-similar color pallette.
 
But what does it matter, really? My worn down opinion of crystals don’t even factor into how i feel about this new jagged branch of this wretchedness.

@PonyPon  
I don’t understand.

@Ihhh  
In this series, for a while.
 
Pay attention.