From everything I’ve read, the reason why Black people and other POC are overwhelmingly supporting Biden is a combination of both your theories.
First you have to realize that POC may be Democrats, but that doesn’t make them Liberal. There is just as much ideological difference among POC as the rest of the population. You have some conservative (little C) POC, you have some moderate POC, and you have some liberal and left POC. The difference is that unlike white people, the issue of race and civil rights overrides everything else. As a result, you have conservative POC voting Democratic because on the issues of race and civil rights, the Democratic Party is 1000x better than the Republicans. These people may be against abortion, they may be against gay marriage, but the issues of race and civil rights beats everything else.
Additionally, because black people and POC have been screwed so much politically, they’re very strategic and pragmatic about who they vote for. In the 2008 race, initially black people and POC supported Hillary. It wasn’t until Obama started winning some primaries and started to look like a legit candidate that he started getting support and endorsements from POC.
In the run-up to 2020, Biden is the strategic choice and is most “electable” (if you buy that argument). Black people and POC are supporting him not only because of what @thewhaleshark just wrote but because the general consensus is that in order for Democrats to win in 2020, they need White Rust Belt State voters, and the candidate who appeals most to them is Biden.