I don't think the two are fully related, at least not causally. If 1-3 are true, then there should be a large enough pool with things in common to avoid loneliness. If this specifically means sexual/relationship loneliness than, yeah.
Third spaces going away and moving a lot online has definitely had an impact on people hanging out outside of much more niche groups. I don't care for organized religion much, but people of various backgrounds worshipped together. People had volleyball and other local leagues made up of all kinds of people who saw a flier for it. Men (not sure if women had something similar) went to fraternal order of the whatevers. Hell, dad and I went to Commodore computer enthusiast meet-ups. I think the loss of things like that has been bad for a number of reasons, including loneliness.