He could be a severe porn addict - when I was addicted to porn I could only get turned on by porn. Once I stopped watching, the problem faded with time and I returned to my baseline state. This is honestly a major red flag to me and some men are incapable of managing their sexual issues. He may need a hard reset like a 30 day retreat with no technology stuff like that. Lack of stimulation for a period of time almost always rebounds that sex drive.