To be fair to people in the US, this is because Bernie and all who followed have referred to themselves as DemSocs when they're SocDems. As someone who studied PolSci this has annoyed me since the beginning, but at this point it's too far gone to do anything about it.

That's about where the political vocabulary in the US stands. 10 years ago, supposedly educated journalists were calling Bernie Sanders a democratic socialist. When asked about it I wish so hard that he said "no, I'm a social democrat, but for most people that distinction isn't important right now", but he leaned into it and here we are.