Why Daniel is so into Bridget?

A similar thought crossed my mind but I think it is largely down to HIS ego. He is genuinely fond of her I think because she is fun to be around and is the only one that laughs at his jokes but at the end of the day he appears to like breaking her resolve not to mention getting under Mark Darcy's skin by interfering in their affairs.

Daniel clearly has no problem getting girls but he really likes the challenge of re-engaging Bridget's interest knowing she can't stay angry for very long. He's basically a player. He didn't think much of her though to callously cheat on her in the first film. Maybe he had something to prove to himself by getting her back into bed which almost happened in the sequel had the Thai Ladyboy not turned up!

"Has anyone seen my wife?" - Columbo

Based on the first movie alone, since I'm unaware of anything in any books or other movies:

- She's easy.
- To piss off Darcy.

I wouldn't say he "always ends up at Bridge." I think he always winds up with a variety of women who are easily and cheaply available, one of whom happens to be Bridget. In the long expanses of time when he's not present in the story, he's presumably busy with other women.

because bridge is willing to go back to him.

he likes girls with squishy stomachs.

must be the illegal sex act/s. :)

I think it was because she was good in bed and let him do what he wanted. He also had the upper hand in the relationship. Lara was totally opposite of Bridget and it was clear she wore the pants in that relationship. She wasn't grateful to be with Daniel and didn't put him up on a pedestal like Bridget did. When he went back to Bridget it was after he was dumped by Lara, so who better to build up his ego. I don't think it had anything to do with Mark. The first time he got an inkling of a relationship between them was when he turned up at her apartment during the birthday dinner. I do wonder if that's why Mark started to be into Bridget. He went from disdain to being into her rather quickly. It seemed like it happened after he saw her with Daniel at the book launch.

After the fight, Daniel says to Bridget, "Let's go up to your place". She then asks him why he wants to be with her. He replies, "If I can't make it with you, I can't make it with anyone".
Short answer: she has been a very easy booty call.

I think he genuinely liked her, but was a player by heart. He liked getting model chicks way above Bridget on the beauty scale, but Bridget was still the most fun out of all of them.

And then once she gains more self respect, leaves his office, and gets famous, he really starts to miss her.

Then when his engagement breaks off, he's lonely and goes back to someone he knows he can woo again. Pretty much like any other person who is lonely. lol

Coz its poor writing & very unrealistic nonsense. You shouldve noticed that