Most of the previous villains’ deaths were not their respective Spidey’s fault either. It’s a CBM trope that the villain has to die at the end, but the hero can’t be responsible so the villain needs to screw up and accidentally kill themselves in their zeal to kill the hero (the somewhat less common alternate path is they have a moment of clarity and redeem themselves by sacrificing their life to undo their villainy). I think the apex of this ridiculous have-cake-and-eat-it-too approach to killing off bad guys, but keeping the good guys’ hands clean was Batman’s ridiculous justification to Ras Al Ghul when he left him to die on the runaway train in ‘Batman Begins.’