At first I thought electricity. But now I think it’s pressure from the bar of metal on the left. It has a curve at the end, and the blade on the right appears to be at a very certain angle. Together, the two forces act to extrude the wire at the perfect angle to make a spring. Just a theory.

There's some magic going on here. After the end loop is created and just before the coil knife comes in the loop moves up slightly with nothing touching it. So maybe there is some electromagnetic field at work, but that just makes it even stranger.