I think a potential factor is the democrats' anti-gun rhetoric. It's explicitly designed to cater to white suburban moms, i.e. those who think guns are bad and scary and threaten their children. This in spite of the fact that twice as many children die from accidents involving glass tabletops than firearms accidents [0]. Add to that the recent surge in new minority gun owners due to safety concerns [1], the long, racist history of gun control [2] from army/navy laws to those targeting "saturday-night specials", and the recent push to lock certain weapons behind a $200 tax and an arduous process [3] and I think it makes for a big factor in Trump's increased black and hispanic support. This is in spite of the fact that Trump is absolutely terrible as far as gun rights go, but the democrats for some reason insist on being worse. Running on a platform of repealing the NFA, the GCA, and the FOPA, or even getting rid of the Hughes amendment, would probably yield massive dividends.

[0]: https://www.ammoland.com/2020/11/twice-as-many-children-die-...

[1]: https://www.blackenterprise.com/black-americans-now-account-...

[2]: https://thehill.com/blogs/pundits-blog/civil-rights/347324-t...

[3]: https://joebiden.com/gunsafety/