Biden is in the politics for decades, there is more then plenty of pretty damning evidence to show that, at the very best, he doesn't believe in anything he says.
Your claim is also invalid on its face—the election theft narrative is being spoken about endlessly. Trump's claims are headline news every single day. A significant fraction of the population believe it. So to claim that the story is being "censored" is simply wrong on the facts.
Hate to be the person to point that out, but let's be honest with ourselves, if it was Trump Jr. who was taking pictures of him putting his dick into a pizza while smoking crack with random hookers, it would be probably retweeted by @jack himself lol.