Just guessing from the replies, (I'm personally not that critical of Pete)
He used to be more left wing, had a deep appreciation for Bernie Sanders growing up, then he had a more right-ward turn. He worked as a consultant for a very unpopular and influential company (Mckinsey) for a few years, then he joined the Navy and was deployed to Iraq and Afghanistan. Lastly the shenanigans around him very narrowly beating Bernie in the Iowa primary of 2020 probably all contribute to the negative sentiment.
None of these really make him worse than even more corporate Dems like Pritzker or Shapiro, so I'm guessing the antipathy is almost entirely because of 2020.