Given Satan's current situation, he can't just leave on a whim.
The bigger the operation, the more things there are to handle. There are transitions with the Angel Mercenary Corps after the battle, and explanations needed with Ivan and Uriyangko, and so on and so forth. Handling these trivial tasks means it won't be until the next day before they're done.
Even then, leaving isn't an option. Just dealing with the passports and visas for Satan's members will keep Little Donnie busy for quite a while. Rebrov is heading to Moscow, and Peter is going to America, so both of their passports need to be made. And as for the Black Demon's group, their identity issues need resolving. Whether they're heading to America or Yemen, they still need a legitimate identity.
In the current state of Satan, it's a small group, but it's a purely multinational corporation, so these days, Little Donnie is the busiest.
