I think the big issue was the "margin of error" in many of these cases. For example, when Quinnipiac did a poll a few days before the election [1], they said Biden was winning Ohio by 4 points with a +-2.5 point margin of error... which happened to be very far off. And this wasn't isolated-–if memory serves me, Wisconsin was even further off?

[1] https://poll.qu.edu/florida/release-detail?ReleaseID=3683