I usually wait for the immobiliser light to stop flashing but not always. It really should not make any difference. If the engine turns over the immobiliser is off so the only other possibility is a second or two delay for the fuel to the injectors to arrive at pressure, in that case the engine should crank a couple of turns more till fuel arrives. The ECU would also require a couple of microseconds to read the sensors: again that should not stop the engine from starting.
My guess is either that you arrived at a very unusual set of parameters that triggered a bug in the ECU program or that you have a sensor that had temporarily lost contact, or giving a reading that was outside normal parameters, to the ECU. By forcing it to start with easy start spray you somehow triggered the system back to normallty.
I would think that the most likely culprit would be the MAF (Mass Air Flow) sensor or the connections to it.

Peter

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