You show very little understanding of US politics in that post if I may be so bold. Joe Biden has been a centrist throughout his career. He's always been popular among the unions that are vital to winning the rust belt in the Midwest that killed Hillary's chances 4 years ago. Sanders and Gabbard are vastly to the left of Biden - Sanders wants medicare for all and a green new deal. I don't know enough about Yang to comment.
I think it's perfectly plausible that Trump wins again. I also don't think Biden was the strongest candidate this time around by a long way. But your argument seems to revolve around the Democrats being too left wing and out of touch with the American people, and then in the same breath suggest that Sanders and Gabbard are more in touch with the American people - seriously? This is a country that sees socialists in the same way as anarchists.
There is also no way that Biden is more 'erratic, racist and stupid' than Trump. He was a longtime member of both the Senate Judiciary Committee and Senate Foreign Relations Committee, serving as Chairman of both and ranking member in between (when the Democrats didn't hold power). He was also Vice President for 8 years without serious incident. He has always had the ability to put his foot in it and has some very unhelpful views on race (as you'd expect from a nearly 78 year old white man) but his opponent promotes white supremacist content and has been recorded bragging about sexual assault. Compared to a competent politician, Biden comes some way down the list of desirable presidents (he barely got out of the starting gates on two previous runs for President) but compared to Trump, Biden is like manna from heaven, which is more a damning indictment of what Trump has done to the presidency than it is of what Biden brings to the table. Who'd have thought we'd look back on the days of Dubya with fondness?