If the 'anti-trump coalition' consists of people voting entirely to avoid a trump presidency, why does the coalition building only consist of capitulation to the views of the anti-trump republicans
Because a split on the left, in this case, guarantees a right win. You should, however fight for what you think is right on all days of the year, not just on election season.
If "we have to vote trump out of office" is the platform and everything else is immaterial, why not run a more progressive campaign instead of trying to win the vote of people who won't vote Dem again
Because biden is not progressive, and since votes on the left are not realy going to trump, he is trying to win votes at the "center-right". To the risk of loosing some votes on the left, yes.