I remember seeing another thread of this- Have you ever attacked anyone in MvM? because it might be a revenge attack.
As for the MvM building causing attacks on pacifist mode, I would say no, that couldn’t be how it works. My city has a Bloon Research lab (for some reason) and I’m on Pacifist. I never attacked anyone, or had anything to do with MvM, and I haven’t lost any money.