Clearly Dean Phillips ran against Biden in the primaries.
Also, Dean Phillips lost to Biden in the primaries. Including in NH where Biden wasn’t even on the ballot but was a write in. There were 22 candidates on the NH ballot. Nothing stopped them from being there. They all lost to Biden who wasn’t on the ballot and had to be written in.
Dean Philips was also advocating for Biden to drop out and then for a new selection process.
This was the real problem. Internal infighting within the party in public. Even a small amount of Democrats actively campaigning against the Democratic candidate was a huge problem. One that the longer it continued would create a larger and larger problem.
Democrats campaigning that the Democratic candidate cannot win is a self fulfilling activity. Even if it isn’t a majority.
Fortunately, the party seems to have resolved that. With a little grass roots help to nudge it back on the path.