I believe your fix - the ECU can only pick up the signal from this 2-wire magnetic pickup if the voltage generated by the magnetic field is high enough for it to be detected. This is the problem with variable reluctance sensors such as the one in the distributor or an ABS wheel speed sensor on some modern cars where it will rust jack and then the gap will be too big and you will have signal dropout at low speeds. Essentially, the ECU was just thinking that the engine wasn't turning and therefore wasn't creating spark.
A fairly good chance that you'll be alright here now, but if you have an issue in the future it's going to be either this pickup or the ignition box. Hard to say which.
Glad you have it fixed.
