Besides the fact that it’s wrong, They are hoping to start a trend that eventually get Trump removed in all states, or as many swing states as possible.
Also, they want to suppress republican turn out in contested races down the ballot.
They also want to increase the popular vote margin for democrats so they can make that argument.
And if you take Trump off a ballot, it may further fracture the national vote because other candidates will get on the ballot to replace Trump.
Djt is on my primary ballot here in Washington