Trump didn't receive an increase in the overall black vote overall in 2020. What Trump won was a 2% increase in the black
men's vote, keeping in mind that the the vast majority of black men and women were key in President-Elect Biden's beating of Trump.
BLM showed the world the police abuse blacks faced, they brought thousands into the street in protest, brought up the issue of police reform and systemic racism to the forefront. Trump and the Repubs might be in denial about systemic racism, but until they face reality, they'll never garner more than a tiny percentage of the black vote.
BLM beats Trump and any Repub president. Americans know the best path, the authoritarian, ironfist, use your batton approach, or gee, maybe the BLM has a point...
"...A majority, though [All Americans], hold favorable views of the Black Lives Matter movement, 51% favorable vs. 38% unfavorable. That favorability rating far outpaces Trump's own; an earlier release from the same poll showed 40% hold a favorable view of Trump, 56% unfavorable. Democrats largely view the Black Lives Matter movement favorably (83%), about half of independents agree (50%), and among Republicans, just 17% say they have a favorable view..."
"...And a majority of black voters said racial relations have gotten worse under Trump, 55% said they face more racism in their daily lives than they used to and 80% said Trump’s election has made people who hold racist views more likely to express them in public..."