Trump is obviously sick. Other Republicans can't even use that excuse

They are mostly sane enough to know irrational behavior when they see it. Many of them are malicious enough to find rational reasons to pursue policies they know will harm millions in order to advance their own agenda, but that is different. That is simply evil. Trump is disconnected from reality, and most congressional Republicans know it. They also know that if there is one person in the country who no one can afford having be disconnected from reality, it is the President of the United States. Malicious people might steal from their neighbors but they don't blow up the whole neighborhood they themselves are living in. That would be irrational, and Trump is fully capable of just that.

I am willing to believe that many elected Republicans (not all but probably most) never really grasped just how sick Trump is. Yes, they knew he was sick of course, but they previously didn't appreciate how utterly toxic a strain of illness he had. They thought if Trump just got his vanity stroked in the spot light, that would suffice, and they would set the political agenda for his presidency since Trump is too lazy to do it himself - in any depth beyond that which fits in a Tweet.

They were wrong. Trump actually believes he is President, and that he is never wrong about whatever his gut tells him at any instant in time. His instinct is to show them all who's boss, and that is truly terrifying under the circumstances. Trump is seriously dangerous and, as politically inconvenient it may be for them to acknowledge that, elected Republicans therefor have a fundamental responsibility to say so and act accordingly.

Trump is of course unfit for office and he must be removed. And Trump can only be removed if Republicans cooperate in doing so. Each day that any one of them refuses to do so just makes them that much more liable for all damage to our Republic, and deaths that occur in this world, as a result of Donald Trump's illness. They don't have the cover of mental illness to fall back on, just short term political expediency to justify their complicity in this escalating tragedy. That makes them more reprehensible than Trump..