Given how the Skyway collapse is burned into the local consciousness, I suspect some of the benefit comes from their visibility.
I truly don't know how the dolphins would fair against a massive ship strike but I can imagine them doing their job.
(ship passing): https://pbs.twimg.com/media/FPgQhy2X0AE8yw1.jpg
I don’t think that is likely? My intuition is that in order to stay seaworthy ships are constructed with more integrity than that.
I don’t have any hard evidence though, just that I have looked at many ship collision/allision aftermath photos and what you describe is not a failure mode I have seen so far.
but only on per-pillar per-direction and with quite a bit of distance between it and the pillar
one some pictures you can see that the ship barley missed one of them due to the angle it was going at
https://en.wikipedia.org/wiki/Sunshine_Skyway_Bridge#/media/...