He is hopeful that he will win, but he doesn't think it will happen.
Can you be hopeful of something happening even though the chances are very bad and you don't think it will happen?
Yes. But more natural English is eg He hopes that he will win, but he doesn't think it will happen.
New words, one handy idiom, and a 2-minute quiz — delivered to your inbox to keep your streak alive.
Yes.
But more natural English is eg He hopes that he will win, but he doesn't think it will happen.