what I got so far thanks to Lexzah's help

Well maybe this guy made a deal with the demons a time ago, helping them be unleashed upon the mortal realm. He was gifted with limitless power in return.

And at the same time they pushed all the angels away and banished them\locked them up maybe.
Or greatly reduced their numbers

So lets say in the last 150-200 years?

the demonic presence hasn't really shown itself more, rather there's been a spike in crime instead

The demons are working behind the scenes, using humans to do their bidding.
 
So the crime lord known as Monocle was bent on gaining power, so much in fact that he formed a pact between himself and a demon lord that succeeded Satan called Abbadon.

Immortality and Demonic Power to be exact, his new found power allowed him to tighten his grip on the underground crime ring, as well as crush his enemies.

Meanwhile the demons after their victory over the angels and setting themselves up on earth, have been working towards another goal.

The demons have been using malevolent humans, influencing them to commit acts that'd more than jail them, demonic cults began rising up one by one, taking sacrifices and feeding their demon masters with power and undying allegiance. And the angels? I have not idea what they're up to.

Angels have been beaten and taken away to a planet on the outer rim of the galaxy called Sil Ethis which is guard by an acient alien race that saw the demons as gods and worshiped them, the gates to heaven locked up tight in demonic chains denying entry to all.