They didn't do it so many times. And Pelosi did not want to do it at all, she held them back and ultimately screwed them up, particularly the first one. Intentionally.
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Trump has been trying to arrest all his political opponents, many which were former allies of his. He's been threatening to do others, including even Obama lately.
Such moves and others have been getting thwarted lately. With his massive unpopularity continuing to grow, his sycophants are fully aware that risking their own futures in order to align themselves with him isn't exactly the best move. They don't want to spend the rest of their lives in prison for the sake of someone who doesn't have that much time left. Guy is literally decaying in front of our eyes.