#but the mystery twins as a whole is a comparison/reflection to the stan twins so i kinda understand where they were going

[danersion]

I just rewatched Gravity Falls, and it has been on my mind lately.

It's pretty obvious everyone has a soft spot for Mabel, but Bill in particular put her in a bubble where everything she ever wanted came true. I mean, she could handle Weirdmageddon pretty well—heck, she did! He could have just bailed or made her a stone, but she practically had her own penthouse in his new domain. He definitely has a soft spot for the shooting star.

So does Bill see himself in Mabel? They almost had the same sparkles in their eyes when Bill was a kid. Innocent, cute, and also:

"Just a little more summer (she was gonna lose Dipper and not see her friends for years if not forever)" or "He wanted to show the stars to everyone," -they have the same vibes [and the silliness y'know]

Wanting to share something beautiful with the people you care about just once or try to lengthen the time because it will never come again (also I'm really glad people are defending Mabel, she was just a kid).

Bill was just trying to justify that action by fitting it in his narrative, and it does! (déjà vu) So we glossed it over, but now it might be plausible.

tldr: Bill sees Mabel as his younger, innocent self and wanted to comfort her in his twisted way with a little spin to make it sound like it's just part of his plan.