Because Eve M slid the stone down 150ft of rough ice, spinning it slightly so that it started outwards and curled in slightly. A single pound of excess force when it left Eve's hand would have sent the stone too far, and Switzerland would have won the match. But she sent it inch perfectly, and the girls stopped it in a circle the size of a dinner plate, 150ft away.
THAT is why it was stunning !!
If a golfer plays a shot from 150ft and stops it within a dinner plate distance from the hole, everyone thinks it was a great shot. What's the difference, except that the Curlers are playing on a difficult, icy surface?