Giles killing Ben

[Btvs fan]

Given that he said something along the lines of always having to clear up messes, this was probably not the first time either that he'd done something like that.

The writing for Ben was all over the place in Season 5. That never got mentioned again either.

Also apparently they were even looking at him being a love interest at one point.

Yes, Ben (played by Charlie Weber) was originally intended to have a slightly larger role, specifically as a serious love interest for Buffy.
However, the writers adjusted his trajectory during the production of Season 5 due to two major creative shifts:
• Buffy's Primary "Love Interest" Became Dawn: The writers decided that the central emotional relationship of Season 5 should not be a romantic one. Instead, they focused entirely on the sisterly bond between Buffy and Dawn. Because Buffy was meant to pour all of her love, energy, and protective instincts into her family—especially while dealing with her mother Joyce's illness—the romantic subplot with Ben was intentionally dropped.
The Rise of Glory's Popularity: Interestingly, the initial plan for the season's Big Bad, Glory (Clare Kramer), was only supposed to span a few episodes. The production team originally wanted to assess Kramer's performance before committing to her long-term. Because she was an instant hit, her role expanded to encompass the entire season. This shift tethered Ben's narrative purpose entirely to Glory's arc as her human prison

 

[Btvs fan]

@NotASlayer Parker/Riley and now Ben ! The writers really loved the floppy haired douche bag as a love interest didn't they !
Its not stated but Im guessing the Spuffy elephant in the room also played a part too in not having Ben as the love interest.