It's because Satan still likes all the stuff God likes, he just got kicked out.
So he's got like, a super fucked up punisher/batman thing going on where he fails to acknowledge his own faults but sees all the sinners arriving in hell as deplorable, and deserving punishment.
He loves all the murders, rapists, torturers, pedophiles, etc. for who they are, because that's who he is. It's a great big ol' party of everyone doing what they want, including Satan, so, yeah, you might get tortured or raped here and there but hey at least it's all inclusive
Like he got chucked out of heaven but God still asked him to test his son for 40 days and 40 nights. I always thought he was working for God, his job was to test people as asked by God.
God's the fucked up one. Think the devil killed like 4 people in the bible and God killed millions.
I always figured in the story that really, since the adversary was the first one banished, he would probably not be so much occupied with the torture of others. Probably be like, "Welcome to the Shit Show." Assuming you even ran into him. Place is probably pretty full by now.
The Christian Hell mythology is contradictory because it's almost entirely fanfiction, and a much more modern fanfiction than you'd think, particularly in regards to Satan's role.
The long and short of it is that, if you assume the Bible is an authority on such things, Hell isn't this major thing where most people end up because they didn't believe correctly, it's not a physical thing at all, much less a thing populated by torturing demons, and Satan wouldn't be in charge, or the Warden, or anything like that. He'd be a prisoner too.
Even in Inferno, Dante depicts him as imprisoned in ice.
If I remember correctly, the book itself refers to a lake of fire, talks of people going somewhere devoid of God's love, and that's just it. It's absolutely bonkers what Dante's Inferno did to Christian lore.
I'm not a Christian, personally, so it's just an oddity to me.