Trump's promoting the myth that the election was rigged is great news for democrats
Because the more successful he is at that, the less republican voters will vote in future elections, because they will have a greater mistrust of the system, thus less republicans will get elected, and less republicans being elected is a good thing, for the obvious reasons, less tax breaks for the wealthy, more money for the poor and middle class etc.
Trump is sabotaging his own party for his own personal gain, which btw, will never work, he will never reverse any of the states' results in the courts, the legal experts on both sides say that.