@degenerateafro there is also the fact that even though Isaac is a manipulative bastard, he considered Rubia at least a close acquaintance and was kind enough to give her a quick death, so she would not end up a mind broken shell of a person who cannot even function on the most basic of levels, IF she even managed to survive all that time until skelly could "save her".
Whereas Skelly upon learning this, and hearing what the mages would have done to her if she did not die, would have much preferred her to go through hellish torture.
Skelly also knows now that any of the silver goop he puts on himself will carry over to the next run. He could have continued with Isaac and got the goop from the capital, and than reset and start even more powerful than last time and actually have better progress. But no, he is an idiot who obsesses over each girl he comes across to the point he will rather kill himself to try again with no plan, even though each time results in failure one way or the other unless he gets lucky.
i know this is basically affirming what you said, but dangit i needed to rant lol.