You can largely replace "western powers" with "France" here. France is pretty well-known for being extremely cozy with the dictators of its former colonies, so long as they represent stability rather than insurgency and let France have some measure of influence in the country. France is pretty unabashedly neocolonial in its treatment of Francophone Africa.
I'd like to add that it is France who controls Chad's currency policy with CFA francs [1]. Some people say it's a modern mean for wealth extraction from Africa.
Yeah, well a guy who gained power through military force is being challenged by rebel fighters... live by the sword, die by the sword.
What matters is what replaces him, not whether western forces like him. I don’t understand folks who are like “the west is bad, therefore anyone the west supports is bad and their passing is good.”