First, Derek Chauvin was prosecuted, and not just because there was video evidence. Every time a black person gets shot by the police (even when it is justified) we still know about it. There have been other such situations that were investigated. They are not ignored.

Second, George Floyd was not "lynched". It's even debateable if there were even racial motivations to the case. He ultimately died of a fentanyl overdose, and there is video evidence he was out of control at the time. Not to excuse Chauvin, but I'm not going to try to read his mind or judge his character on the basis that "he looks like a white supremicist" sitting in court.

Saying cases exist but we simply don't know about it, is dodging the question. You can't prove a negative. That's just being disingenuous. Where is the proof that lynchings are occuring but they are just being swept under the rug?