IN THE BEGINNING Michael was essentially the heavy hand of the Law. He made sure everything stayed in its place and whatever direction Marie (at the time God) and Lucifer took it in he enforced it.
While he's an ambitious dickhead he's not all that creative, so he never actively planned against Marie outside of the regular Bad Thoughts. He jumped at the opportunity to take advantage of Lucifer's coup against her and turned that battle into an absolute nightmare for everyone.
In the end Michael was the one who fatally wounded Marie and banished Lucifer... and as such become the head honcho of Heaven which he has been reforming into a sort of militarian dictatorship since.
Lucky for him, winners get to write the history books so the prevalent notion is that Michael is a hero of Heaven and Marie is still God, albeit removed from the public eye. No one except for a select few archangels know who is actually calling the shots (Spoiler: it's Michael, he's playing the part of the legislative, executive, and judicial branches simultaneously while making it seem like there is still someone else behind the curtain).
Does he love the power? Absolutely. Does he love the day to day nonsense of running a kingdom? No, he's so over it.
Authors note: Hope he suffers. :)