It doesn't matter what the speed limit was on that stretch of road. The Driver's speed was too fast for the conditions.
When I'm driving in a rainstormHow can you tell it's a rain storm? While it may have been, I could show you my driveway after the sprinkler hits it and you'd think it was pouring., I am looking for standing waterAnd going through a corner at 65mph, you're probably not seeing it quickly enough... Like this guy.. If I can't see well enough to see a big puddle of water in my lane of travel, then I'm going too fast for conditions. Agreed. However, seeing that if he's traveling at the posted speed(65mph) I don't think he could have seen the water pooled even if he were going 45mph. If you're going 45mph in a 65mph zone, I think you're a hazard. =p
If anyone is going so fast that they can't see the road conditions ahead, and react to hazards in the road, then they are going too fast for conditions. Again, I agree. However, sometimes there are circumstances where you'll be unable to see thing until they're right under you. Like hitting pooled water in the downward slope of the apex of a curve.
I also keep good tires on my vehicles, so I know how likely I am to hydroplane, or not. THIS is what I imagine the driver is guilty of.
Bottom line: It is the drivers fault. I'm glad they didn't hurt themselves or anyone else. Totally agree.