I did not say ALL demons are restrained. They are legion.
Specifically, in the bible, the 1/3 of angels that followed Satan are currently restrained and will be let loose during the end times (as will Satan himself after the 1000 year reign of Christ — which of course is AFTER the Tribulation).
Lesser demons are still running rampant, as is Satan himself who is the “God of this world”.
I’ve heard it said that the fallen angels themselves were bound, but the spirits of their offspring with women roam the earth, as demons. The Ethiopic Enoch backs this up. I don’t necessarily accept or reject this explanation. It’s not counter to the Bible but it’s extraBiblical.