I mean, Elizabeth Warren was probably more known Bernie Sanders was in 2016 and it's not like people forgot about her in the interim.
There were 20+ candidates this time around and we ended up with Joe Biden and Bernie Sanders. That could be name recognition, but that doesn't explain why Warren and Harris floundered while unknowns like Buttigieg and Yang managed to survive for so long. Hell, I even know who Tom Steyer is now. It seems like it's not name recognition as much as it is reputation recognition, which only men seem to get in a positive way (e.g., Clinton's infamy) despite the fact that there are plenty of well known women politicians with qualified resumes.