Well they were certainly both greatly harmed by their campaign headquarters/internal documents being hacked, so it's an apt comparison. The difference being that McGovern still would have lost anyway without Watergate. He probably would have done about as well as Mondale did in the popular vote at least, and maybe won one or two more states (Rhode Island, Minnesota). Whereas Clinton, in a world where Vladimir Putin chooses to do nothing to influence the election, wins at least Michigan, Wisconsin, and Pennsylvania, and probably also Florida, and possibly North Carolina and Arizona.
Trump woulda won anyway. Also, in NC and AZ, it's practically impossible that spreading fake news could influence any final state's results, let alone swing it from +3.5 for Trump to at least +0.1 for Clinton