The state law against committing crimes to influence an election doesn't need to supercede the federal law - that's not how the 10th amendment works.
The election that was interfered with was the state level election that citizens engage to select their electors, since our system has no actual federal elections.
The law violated was NY 17-152, but the jury didn't need to know that because that finding was from Michael Cohen's case, and was only one of three other crimes we know he committed as Individual #1.