You can see it is a property issue when you look at this scripture:
*** Rbi8 Deuteronomy 22:22-29 ***
22
"In case a man is found lying down with a woman owned by an owner, both of them must then die together, the man lying down with the woman and the woman. So you must clear away what is bad out of Israel.
23
"In case there happened to be a virgin girl engaged to a man, and a man actually found her in the city and lay down with her, 24 YOU must also bring them both out to the gate of that city and pelt them with stones, and they must die, the girl for the reason that she did not scream in the city, and the man for the reason that he humiliated the wife of his fellowman. So you must clear away what is evil from your midst.
25
"If, however, it is in the field that the man found the girl who was engaged, and the man grabbed hold of her and lay down with her, the man who lay down with her must also die by himself, 26 and to the girl you must do nothing. The girl has no sin deserving of death, because just as when a man rises up against his fellowman and indeed murders him, even a soul, so it is with this case. 27 For it was in the field that he found her. The girl who was engaged screamed, but there was no one to rescue her.
28
"In case a man finds a girl, a virgin who has not been engaged, and he actually seizes her and lies down with her, and they have been found out, 29 the man who lay down with her must also give the girl’s father fifty silver shekels, and she will become his wife due to the fact that he humiliated her. He will not be allowed to divorce her all his days.
Married (owned) death
Engaged (owned) death
Single (not owned) sold to her rapist
So sexual immorality was not a capital offense if the women was single, not owned by a man. What was bad was not the immorality but that the man attacking (or seducing) the woman with a husband or a fiancee was stealing that man's property.