I think the sacrifice is symbolic. Yes, he could have done a bunch of things that would have much less impact on him. He could resign and then lawfully stand around with a sign. He could start a substack and a YouTube channel.
Would that make headlines? How many people would that reach? Someone sacrificing a career to make a point makes a point.
Someone operating in a government-approved protest area saying protest things that the government permits is a much less significant protest.