“The Bible repeatedly and emphatically claims there are indeed demons.”
I grew up with missionaries living in our house when they were back in the states during furloughs. The stories they’d tell about demonic activity — and actual demons — were terrifying. We kids weren’t supposed to hear it, but upstairs, supposedly in bed, we’d lie on the floor with our ears pressed to the registers and were able to hear everything. Then we couldn’t sleep. :(
There are many cultures which are especially receptive to demons, and they often attract missionaries, too. The USSR was well behind the West militarily, so officials and scientists deliberately cultivated demonic “help,” looking for an edge, with predictable results.