the ecu *should* set a code for the crank position sensor if it doesnt see a signal from it during cranking... but unfortunately it doesnt always do so, and thus making it slightly more difficult to diagnose fast.
same goes for the cam sensor too unfortunately.

considering you went from having weak spark, to no spark.. i too am thinking you should be checking wiring - mainly grounds. it very well still could be a sensor, but id start with the wires.