Overthrowing Trump is such a popular topic among his adversaries since he won the election surprisingly. So many "turning points" have been claimed by the "resistance" front. So I won't buy this one. OTAH IMHO "turning point" as a concept is enough vague, so IIRC you can claim many prior and posterior events to be turning points.

Not necessarily.

It's not because it's bargaining chips in the search for larger game.

On another note, these investigations are good because democracy can only function if the actors are in general of good intent. Democracy is fragile and can easily be subverted or destroyed from within. So this isn't so much a threat to democracy as it is the system working as intended: branches of government created separate but equal to ensure that everybody plays by the rules.

Finally, it's not partisan because the majority of the people participating in this are actually of the same party that holds all three branches of American government.