There's a phenomenon (fundamental attribution error) studied in psychology which shows that people 1. overestimate dispositional factors, and 2. underestimate situational factors in the behaviour of others. This also comes into play with publicity. Studies show people incorrectly perceive that a celebrity reading a promotional messages likes the brand they're promoting, and completely disregard the celebrity is being paid - even though they consciously know that they are. In studies where someone is forced to read a text promoting a position they don't agree with, participants perceive that the person reading the text agrees with what they're reading - even though they've been told the person is forced to read the text.
You interpret that GOP's members lack of speaking out as implicit approval of Trump's behaviour based on no evidence at all, while disregarding all the factors inside the situation that are preventing and heavily discouraging them from speaking out.