Educate me, please: How did Scott Pioli fail in KC?

See, I thought he should've proved to be a "home run" hire as CEO for football with the Chiefs.

*Owner who believes in chasing hard after championships, as does Bob Kraft.
*Passionate fan base which wants to get behind a winner, as does the New England fan base. Chiefs might have the best fans in the NFL.
*Learned alongside the best HC/czar of his generation, much as I hate to admit that about Belichick. Pioli surely learned from Belichick what "extras" to look for in a player, including whom to draft; when is the right time to "sell high" and get rid of said player; how to manage the salary cap... and so forth

And still, Pioli crashed and burned after a short time. When he did, it quashed a theory I've always believed: Get the best, most-ready candidate from a perennial champion at the top of your flow chart and turn 'em loose. The Demoffs of the world need not apply.

How again did Pioli crash and burn?