It is not well known but there have been numerous scandals which put this trust into question. For example in 2012, a trustee of the Wikimedia Foundation UK used his position to place his PR client on Wikipedia’s front page 17 times within a month. Wikipedia founder Jimmy Wales made extensive edits to the article about himself, removing mentions of co-founder Larry Sanger. In 2007, a prolific editor who claimed to be a graduate professor and was recruited by Wikipedia staff to the Arbitration Committee was revealed to be a 24-year-old college dropout. These are only a few examples, journalist Helen Buyniski has collected much more information about the the rot in Wikipedia.

I don't really understand how decentralization would address the trust and legitimacy problems of Wikipedia. I do see value in adding community wikis to Lemmy, however.