Fear

Apparently, Trump's administration has a number of members trying to manage Trump behaviour through underhanded tactics, like hiding documents he asked to get readied to be signed, because they think that he is mercurial, unprepared, reckless and incapable and unwilling to learn.

Why they don't just step away from the guy and voice for invoking the 25th amendment?

Because they can use him as a tool to get what they want - the tax cut, repeal of anti-pollution rules, the dismantlement of the Financial consumer protection bureau etc.

Also, the 25th amendment takes time;  It is a slow process, who would not remove Trumps' powers for - likely - some months .

Trump still has unfettered access to the "nuclear football";  In four minutes, he can launch a massive nuclear attack and be rid of the judgement of history because - as you may know - history is written by humans that have the luxury items required to write on storable media.

A nuclear Armageddon should eliminate most of the firsts an virtually every of the seconds.

He seems like a raving lunatic in his best day, and has shown a morbid fascination for the USE of nukes as the last embodiment of macho swaggering.

- "Why can't we use them?" , he asked (three times) while they were briefing him on the nuclear attack procedures -

Now, imagine him looking down a removal from power for unfitness - humiliating - or a Clinton-esque impeachment process - more humiliating?- followed by a raft of civil and criminal trials of members of his administration - most of them seem as bent as a three dollars banknote - and staff of his private enterprise - it is not exactly a mystery that many foreign governments and political figures shovel money to Trump concerns as a way to mollify the big guy... efficacious for them, but does not really smell legal, right? - included, maybe, of some of his family.

"Après moi, le déluge" reads very Trumpian, I think. 

Now you feel it?

Fear.