How, look at the polls. Look at the leads Biden has in demographics he won in 2016. Trump is only 6 points up with White males and he won that by 20 points last time.
This is an interesting, informed and non partisan story on the chances of both candidates
https://projects.fivethirtyeight.com/2020-election-forecast/?cid=rrpromo
The Iowa poll is a mess, it suggests that Trump will win a majority of non white votes and by 15% in democratic strongholds,
Axelrod has speaking about this, looks like something has happened to their methodology