Look closely at the surface. That grid of raised dimples isn't texture or grip — it's the working part.
The pad barely touches the ground. It rides on the tips of a few hundred small raised feet, and between every one of them sits a pocket of still, trapped air.
Still air is one of the worst heat conductors available. It's the principle behind a double-glazed window, a down jacket, and every sleeping pad ever made. You aren't blocking cold with material — you're putting a layer of motionless air between yourself and the mass trying to pull heat out of you.
That's why a thin dimpled pad beats a thicker flat cushion at this specific job. The flat one is in full contact with the cold surface. This one is barely in contact at all.
The foam is closed-cell XPE — the bubbles inside are sealed, so it can't take on water. That matters more than it sounds: wet insulation stops insulating, which is the same reason a soaked jacket quits working on you.