You're exactly right and the indictments won't matter to many people.
There isn't much that could come out about Trump that would cause them to move away from supporting Trump. It could come out that he was the leader of some neo-Nazi group and he was involved in the beating of a black guy...people wouldn't much care. Because they really only care about immigration, terrorism, and the economy. IF there were to be a significant economic downturn, THEN people would peel away from Trump.
There is Trump the person...and the things Trump is doing that people like. Most don't care about Trump the person. They don't care if he is a jerk, if he lies, if he is childish, if he behaves in a low manner, if he broke a law, if he's a racist. They have separated Donald Trump the man from the actions of Trump the President. They LIKE the actions by Trump the President- the tax cuts, the crackdown on illegal immigration, the elimination of regulations, the low UE rate, the record DOW, the renegotiation of trade deals, the return of manufacturing, etc.