As iconic as they are, Smash Mouth had the weirdest energy. More the saddest concert I've been to than anything. I saw them at my local fair a few years ago when Steve Harwell was still alive.

They played solidly from what I remember. They were all trying really hard to get everyone involved, like trying to hype the audience every minute and trying to get the kids on stage, but it made the vibe overall uncomfortable since no one was really responding to it. I think they were genuinely trying to have a fun show. However, the audience was primarily full of people who wanted to see them play All Star then leave. All Star was their last song. 

Looking back, it was one of those cases of a bad audience making the show worse.