Ok, Becky lies, but I have to wonder if there aren't some grains of truth to her lies. Pure speculation here, based on my own Autism probably making connections where there likely aren't any, but consider:
Daniel decides to get a second partner while with Becky. She just picked up some greasy dude named Samm and moved him into the family home, so surely Daniel should be allowed a second partner. But whenever Daniel tries to bring this up to Becky, she loses her shit, goes suicidal, screams he's not into her anymore, etc. Maybe she even assured him that after they had a baby together she would feel "safe" enough for him to meet other women for more than a quickie.
Daniel sees that he's become the breadwinner AND the primary caregiver of not JUST a new baby, but also a household of unemployed degenerates after burning out from the mental and physical exhaustion. Daniel maybe even tries to talk to Becky about this. She retorts on Bluesky that no men in the house ever wash a dish and she is Opressed.
Daniel begins talking to other women, technically behind Becky's back, but like, cmon. He is feeling profoundly BABY TRAPPED. Maybe he tells her this in a fight and the words stick with her. They don't really fit her situation, but Becky's gotta Becky.
Daniel falls for this other woman. Theoretically, this should be fine, right? They're polyamorous! Heck, his "wife" is married to another man! But he tells Becky and everything we have seen unfold begins.
Now his friends see that Daniel was actually defrauded in a lot of ways in his "marriage" and maybe understands a bit why he'd want to cut and run (if that's what he's doing, even) outside even if how unpleasant Becky is.
End sperging