Why is Jeremy such a jerk

WHY in the f*** would his character..

1) admit to proposing marriage cause of the apartment.. IN FRONT OF HIS WIFE. he should be bragging to no one IF he is so devious indeed

2) freak out during the fire alarm scene, showing his materialistic side. there wasn't even smoke bruh..

I hate when films make the "husband" into a total dumbass just so it's OK for his wife to leave.
It be better writing if Amy just bailed (showing the scene of her isolated @ the party) BOOM end of story