Not enough votes. That's only one bloc.
Black vote is about 12% of the electorate.
A rise from 8% to 18% for Trump is a change of only 1.2% overall.
But it is concentrated urban and a huge number in the overall denominator is from states with essentially no black vote.
So this talk is mostly about 2.5% of the on the numbers.
2.5% will overwhelm the battlegrounds. Remember, Biden’s lead was 7 million with 5 million from California and 2 million from NY. The concentration of support is extreme.