"Regarding my situation at St Etienne, it was time for me to find another solution," he told l'Equipe.
"I understand that (St Etienne coach Ivan Hasek) does not have faith in me."
Diawara, 26, joined St Etienne from Parisien lower-league side Red Star in 2001 but became surplus to requirements despite featuring heavily last season.
"I'm not leaving on bad terms; there is no problem," he continued.
"I know what I gave to that team. I was difficult to be axed at the beginning of the season, despite all my determination, but I will always respect the boss' decision.
"I am happy to be (at Bolton) and I already know a couple of players like Abdoulaye Meite, who is a childhood friend."