Commercial Malwarebytes isn't on-demand, it's an actual anti-exploit/rootkit solution. I assume the free version, which only has the on-demand features, comes with these components anyways? Might explain that behavior.

My reason to trust them is that they seem to be generally respected still, I've been using them for a long time and they've yet to start annoying me with dark patterns and upsells - of course that's not a super great indicator.