What this means—assuming it’s accurate, and it probably is—is that the end for Trump will most likely come fast, as some sort of tipping point causes his support on the GOP side of the aisle to largely and suddenly melt away. It’s an unstable equilibrium for Trump: even many in his own party hate him, but are afraid to say so.
In effect, their fear is self-justifying; a given Republican congressman is afraid of Trump because they all basically are, and if just one or a few defect, the defectors will be punished. However, once something prompts a critical mass to stop being afraid, suddenly the whole reason for the fear in the first place will evaporate․
Unstable equilibria tend to suddenly collapse; it’s in their nature. In a social system (as opposed to a physical one), the collapse tends to be particularly hard to foresee in advance; the status quo keeps lasting until one day it is insecure and the next it is gone.