Most importantly, you can often find out WHY a campaign exists with stuff like utm=small-biz.
If they’re a competitor, congrats, you just found a potential niche you may have overlooked. If you look at what events they send to their analytics, you can uncover what they know and don’t know about app usage or ad performance.
More usefully though, you can learn a shocking amount about a company from their utms and event data.