It'll happen when this place becomes attractive enough for Black folks that there's a legit, thriving Black community here.
Which, in part, means making the people who greet Black folks with overt and/or barely-disguised hostility on here extremely unwelcome.
It means repeatedly telling lots of racists "we don't do that here" and blocking them. It means telling their instance moderators that they need to do better, and/or blocking those entire instances until they get their acts together.
We need to make this network feel less like a sundown town, where Black people are barely tolerated—and when they are, only to the extent they make the economy function, on "our" terms.
In other words, the people who are willing to overlook anti-Blackness on the Fedi need to finally start putting in the everyday work of improving the culture.