I will die on the hill of him being a decent coach. Nothing earth shattering, but a decent coach and (by most accounts) a good man who tried to get to know the staff and get the players to also get to know them.
But those types just don't work at Spurs. Never have, never will. You need to be a nutcase messiah. You need to believe, make everyone believe. And you need to have political acumen - at least, to the extent of navigating the backroom battles, keeping the fans onside, and keeping the players happy.
All those soft skills are where failed. He'll do well at a smaller club where things are set up like they were at Brentford - where the coach is just a cog, and not an important one.