I didn't watch the debate, but I could probably recreate exactly how it went down with little effort, and your description validates that thought.

The two candidates are just very transparent, in their own separate ways. McKee is low-energy because he knows that he's probably going to win regardless, and because he's just a milquetoast moderate RI "Democrat" with very few ideas and an aim to coast through his term. He knows that he's "the best we've got" at the moment, and that Kalus is basically all bluster, so he's not going to bother expending much effort to beat her, because all he has to do is spout the basic anti-Republican, vaguely-progressive talking points, as this will automatically put him over the edge with most voters.

Kalus, meanwhile, is just an opportunist: she sees RI as an easy target for injecting a bit of the right-wing resurgence Trump brought about in 2016, and she's basically shoehorned her way in because no other Republican would even bother to try and oust a governor from a state that staunchly votes blue (regardless of how barely leftist RI Democrats actually are). She strikes me as something of a grifter, which is evidenced by the fact that she's hardly a Rhode Islander, in practice or in name. She's basically throwing shit at the wall to see if it will stick. If and when she loses, my guess is she'll leave the state and go back to Illinois.