We got Tre White out of that move, and we didn't give up really all that much to get Allen. Plus, Mahomes has Kelce, Hunt, Watkins, and Hill. Mahomes also has Andy Reid, an offensive guru, and whenever Reid has more than a week to prepare for a game, he destroys the other team. Dude is 16-2 coming off the bye, and is 12-8 in opening week
https://www.cbssports.com/nfl/news/sorting-the-sunday-pile-andy-reid-has-a-remarkable-post-bye-nfl-playoff-record/
https://arrowheadaddict.com/2017/09/05/andy-reid-opening-game-week-1-nfl-history-chiefs-eagles/2/
(second article is before their opener last year, when they beat the Pats, and this year when they beat the Chargers)
Mahomes may turn out to have been a mistake, but I'm far from wiling to judge that