Indeed, the switch is a pressure activated switch. It doesn't care if you want to stop, it only cares if the brake system was capable of building and maintaining an adequate pressure.
There are two styles of switches. The older style should have been upgraded, but it's out there. It is a fluid pressure switch. If you removed the switch and fluid came out of the hole, then it's an older switch and bleeding is necessary.
If it's the newer style switch, it's activated by the air assist pressure. There would have been no fluid leakage of any kind when changing this switch.
That said, no pedal is no pedal and the immediate concern is why. If the fluid leakage during the switch change is not conclusive (I can't see why it wouldn't be but you never know...), start with the basics.
First, you need a sealed and contained system.
Fluid level?
Look for visible leaks at any of the wheel ends?
Look for visible leaks along the frame?
Second, you need to fill it with a non-compressible liquid (brake fluid) which includes removing any pockets of air (compressible) trapped within that non-compressible fluid.
See the power bleeder suggestion above for sure. Otherwise, the standard brake bleeding routine applies, except that you would start with the airpack bleeder, and then begin with the farthest wheel from the master and working closer.