It's possible that the skipper thought he had room to clear, but the smaller boats veered into his path at the last minute and he didn't have room/time to avoid. If we had the benefit of an aerial video or photo sequence we'd know.

As the overtaking boat it's still his responsibility to avoid, but that would at least give him the benefit of the "couldn't help hitting that child who ran from behind a parked car" defense. Doesn't clear him of legal responsibility but it at least makes him less of villain.

I won't race a boat I own in a mixed fleet because the first time I raced my first trimaran I had a bad experience overtaking. We had just rounded the mark and asymmetric spinnaker, when a smaller and much slower boat we were overtaking VEERED DELIBERATELY into our path. We were going at least 7 knots faster than the other boat and there was nothing to do but round upwind (made a mess of the asymmetric against the rig). That took us out of the race, but fortunately I avoided running them down. I know it was deliberate because I saw the other skipper turn around and look at us overtaking just before he steered into our path. Needless to say I was really pissed off. That jerk might have caused me to be responsible (under the rules) for personal injury and a lot of very expensive damage to boats.

One-design racing is the way to go -- IMHO.