this luck needs to be earned and Max spent the race exemplary and significantly did not make obvious mistakes. The intrigue in the championship was revived
Yes, Max did everything he needed to do - except putting the car on pole, but Leclerc not starting was the only bit of luck he didn't earn himself.
Yes a bad weekend for Mercedes and Hamilton. All teams make mistakes sometimes, it's just that Monaco is the worst place for this to happen, but overtaking is almost impossible... and Mercedes made it even worse by messing up the pit stop timing, and so preventing Hamilton from maybe finishing fourth. Any other track, Hamilton would, you'd expect, quickly overtake the other challengers and get right up behind Max into second... but Monaco? No chance.
As you say, it really sets the championship on edge again. I do think this was simply a bad weekend for Mercedes at the worst time, and their car does in general seem to be improving. We will find out at the next race!