[comex]

> The Democratic Party proved it was not as progressive as they thought as Sanders lost the primary.

The FiveThirtyEight forecast for the Democratic primary [1] gave Biden the highest chance of winning for most of the process. He did have a steep drop in the month before Super Tuesday (followed by an equally steep rebound), but still, I wouldn't say the forecast was especially bad. That said, polling is always worse for primaries than general elections, since there are more candidates and fewer voters.

[1] https://projects.fivethirtyeight.com/2020-primary-forecast/