Historically great based on what exactly?
He led the league in INT% (behind Penix but he only played 9 games) and his season was 33rd all time. In 2024 he was third in the league.
He fumbled 9 times, which was more than Hurts, Maye, Allen, Herbert, Lawrence and Dart despite those four all having more rushing attempts than him. All four of those guys got sacked more than Caleb as well. Best I can tell, the Bears fumbled 13 times but only lost 4 of them.
Meanwhile they lead the league with 23 interceptions despite not being the best defensive team.
Don't want to make it seem like Williams sucks. He may very well turn into a superstar. I just don't think we know that Caleb is a guy you win because of while Maye isn't (though it's certainly possible that sentiment turns out to be correct).