You seem to have forgotten what we were talking about. You claimed that religions tend to survive. I was using the religions in ancient Rome and their lack of survival (except Judaism) to point out that no, they don't tend to survive.
I think I said religions tend to survive longer than civilisations and certainly nations. Dicky Underpants, correctly examining failure of Mithraism said that part of its failure is it did not appeal universally. He was correct in that he didn’t view it only in terms of Christian political success, Something Christianity did without until Constantine and has done without from the advent of secular states like the US and France.
With Constantine we see the phenomenon of the religion of the King being the religion of their nation
. A kind of national religion. National religion is an easier affair IMV than personal religion since you can let a society believe for you. Whether that is proper religion, I have my doubts.