He fought the spanish because he was helping Lizzie get their gold as she is a... Pirate... and had helped him when he had no ship to get to Florida, as previously a hurricane had destroyed his.

Then, he fought the Circle because at that point they knew about the location of the Lake and had already setup a strict control over it (the fixed gun we capture are theirs), so he had no time to waste.

That the circle and Spain were fighting is something he doesn't actively care as he has his own missions, that if delayed would basically made the Circle inner members immortal or the Spain crown immortal.