Bad luck, and Hobie paddle.

What model of Hobie? I can not grasp how a mirage drive arm can break unless someone it trying to get one up on plane.  Kayaks are displacement vessels with a maximum hull speed. Once you reach that speed, it is next to impossible to go any faster.  Therefore the harder you push, the more energy you waste and the more likely you will have a catastrophic failure.

Nothing out of the ordinary, just open ocean fishing. From what i hear the arms are actually pretty weak, and break quiet often.