The real reasons why the wiki is no longer official (because everyone seems to have their own version of events) is here, but here’s the cliffnotes:

• Mojang/Microsoft’s legal team contacted them notifying them that the contract they signed with Curse in 2011 is being terminated (probably because Curse was no longer the owners after being bought by Fandom)
• As a result, all of the official logos/artwork/anything copyrighted by them could not be used legally.