It is simple to understand why the 1st World woman with little possibilities would buy the reasonably attractive viral 3rd World man. Perhaps not as simple as why he sells himself.
In many cases, the third world man has run out of options. He has gone as far as he can go in life, and sees no future. He probably had dreams, but now occupies a low level life with many lacks.
The idea of living free, no rent, no bills, no obligations looks like heaven. The idea of going to a 1st World Country where everything works is a dream.
He has probably had a lot of sexual exploits, possibly fathered children which he has to support. His salary doesn’t go far.
He doesn’t mind having a wife who will be the “Man” of the family, who will deal with bills and repairs and purchases and problems. He is happy to leave his country and maybe get the childhood he might not have had.
Whether he is fully aware of his situation, whether he believes that somehow it will improve, or that his wife really loves him, time will tell.