When a congressperson leaves office, what happens to their staff? Do they get picked up by the winner or are they jobless?
If the Congressperson is replaced by another from the same party, it's possible that the new one will pick up the staff. And occasionally someone will cross parties. But they usually have to go and look for a new employer. In some cases, this means leaving politics, as these movements tend to happen in groups. For example, this year, there was a small movement towards the Democrats. Although some staffers may catch on with the Trump administration.
In 2010 and 2014, there was no presidential change and the movement was towards the Republicans. So many Democrat staffers were unemployed. In 2006, the same thing happened to Republicans. In 2008, Republicans lost in both Congress and the presidency.