always said this guy was an uncharismatic loser
That's going too far. He clearly proved he's a winner last year... But like many coaches, he requires an already built and well-oiled machine to do well. He was perfect with last year's team, providing the tweaks needed to take it to that next level...
...but when things aren't ideal the guy is just not the right fit as a coach. He doesn't have the ability to organize, discipline, and inspire a squad full of new faces, weaker dressing room personalities, etc to have the grinta to dominate like a Conte or Simeone can do. It's really too bad. Combining Allegri's European tactical nous with Conte's energy and determination would make one of hell of a coach.
The good thing for Conte is that tactical nous can be gained through experience. The bad thing for Allegri is that a coach's personality really can't, and I doubt he will ever do well in less than ideal circumstance. It's really too bad we couldn't keep our team together for one more year, while adding just a couple pieces, instead of the ridiculous wholesale changes. No departures, bring in just Dybala to learn from Tevez, Alex Sandro to rotate with and learn from Evra, and a trequartista so Vidal could return to midfield and I really think we would have been dominant again this year under Allegri.
It really was Marotta's job to convince Vidal and Tevez to stay on for one more shot at CL. I'm sure Tevez leaving played a part in Vidal's decision to jump on the chance to go to Bayern. He probably saw this as a rebuilding year.