It's because being likable and personable is the most important thing in a primary at this point in time. Biden is somewhat personable but he is also actively telling people to fuck off if they don't like one or two of his positions.
"What about Trump?" is probably a counter to that thing about being likable and personable, but most of his supporters are sociopaths or people who at best have had life-long problems with caring about other people. So he fully represents them.
Also, it should be noted that the right wing smear machine works and they were able to make up shit pretty easily about Biden. It's not as easy to do that with the other candidates because their sons were not offered jobs they were plainly unqualified for. Even though Joe Biden had literally no involvement in that, the average American is pretty easily led to believe falsehoods. Having a great campaign structure isn't enough to carry someone over the line in the face of those things. It's going to be hard for them to make up shit that sticks on the other candidates. Telling people the healthcare they love will be taken away isn't good enough when fucking everyone hates their health insurance provider.
"What about Trump?" is probably a counter to that thing about being likable and personable, but most of his supporters are sociopaths or people who at best have had life-long problems with caring about other people. So he fully represents them.
Also, it should be noted that the right wing smear machine works and they were able to make up shit pretty easily about Biden. It's not as easy to do that with the other candidates because their sons were not offered jobs they were plainly unqualified for. Even though Joe Biden had literally no involvement in that, the average American is pretty easily led to believe falsehoods. Having a great campaign structure isn't enough to carry someone over the line in the face of those things. It's going to be hard for them to make up shit that sticks on the other candidates. Telling people the healthcare they love will be taken away isn't good enough when fucking everyone hates their health insurance provider.