I think you're mostly listing ways that both insect and flower could survive before they both developed specific adaptations that aid in their mutual interactio

I think you're mostly listing ways that both insect and flower could survive before they both developed specific adaptations that aid in their mutual interaction. But I feel like the more satisfying answer is that very gradual changes in both species can eventually lead to two species that appear to be extremely codependent. In this case, I would guess that even the tiniest proto-flowers that resulted from random mutations could just so happen to be discovered by insects with the tiniest random mutations that led them there.