I understand why they felt that way. The civilized world has been tolerating uncountable violations of oath of office by trump and his administration for 4 years by that point. What they failed to grasp is, yes, there is a line that you cannot cross without consequences. You cross that line and suddenly all of these people who have been struggling to accept everything are mobilized to action. The trumpers think of everyone except themselves as a bunch of sissy pushovers, so I think they'd be pretty surprised when the line was finally crossed.