Chuck wasnt right about everything. Jimmy wasnt the reason their Dad's store went bust, and he never owned up to completely hating Jimmy most of his life. Even in the end saying "you dont mean that much to me" it was a lie.
Chuck is a piece of shit. Theres a reason their mother cried for Jimmy in her last words, and why everyone likes him even Howard

I will also add Chuck's mental illness starts not after the divorce but after he finds out Jimmy passes the bar