why are Iranians celebrating that Joe Biden is president?

Answer 1

The world getting closer to solving the Jewish question. 

Answer 2

Why shouldn't they? We need to treat people right. Trump tried to start a war with them. Tore up the treaty the world honored while all you   people want is trouble. Instead of him sniffing after deadly dictators he destroyed the unity Obama and Biden had with a  nation with some problems. We have some too.

Answer 3

You don't have to be a friend to welcome the fact that the guy with the nuclear codes is no longer a complete asshole.