losing someone special to them weakens their power. its like losing your other half if you lose your mate. they are deity, they may die but not their soul that is strongly connected to someone they cared for. and sending the ten deity on earth to make babies* to form stronger bond cannot be done unless they are officially tied up together or atleast knotted together.
think about this, the older loong on earth wants to spend his life with the other loong because he thought it is the only way to get back to heaven, but he didnt think fully of what's the purpose of the bond they are making. he ask for marriage, but their commitment to each isn't deep as they thought it is. the other still have doubts and also losing interest in making it back to the heaven, because he accepts that he is no longer a deity but a human living on earth with a drunkard father.
you see, to form a stronger bond, trust and faith is the very first key to make it work, then love comes second, and farther more.
you got one thing wrong. they both started out thinking they would be able to go back to heavenly realm but they BOTH fell in love. they both stopped caring about getting to heavenly realm as long as they were together. they both said as long as they could live together happily on earth it doesnt matter. gold loong proposed him bc gold loong couldn’t imagine a future without him whether it was in heavenly realm or earth
lets face a fact that most people confuses love in other aspects such as responsibilities, respects, care, etc.., love isn't all about fantasy
if you still remember it correctly, they hit off immediately after they find out they are both deity. one, still believes that they'll be able to go back to heavenly realm and the other one had already given' up.
my theory was about strong bond of mutuality that must be built between each one of them, not just love itself.
i think jin loong sends all the ten deity on earth to be safe from the approaching revenge of *i-forgot-the-name*
he knows he's getting weaker as years goes-by and his ability to hold back the enemy gets weaker too, hence he decide to make a sacrifice. sending the other deity to have baby is like making a stronger bond between every deity. the stronger the bond they make, the stronger power they contain. jin loong gets weaker because he lose someone *that-one-might-be-someone-special-to-him* i think my explanation is crap, sorry
Hahahaha they're so embarrassed taht they turn into animal to save their as*es