Quote:

Just wondering if it is the crank sensor, why the light didn't come on



The light is just warning device. If the subject sensor / circuit stays within it's designed operating parameters. The light will not come on by design.
Crank sensors operate in a .5 to 4.5 volt range .
IF it goes above or below this voltage scale it's sets a fault and turns on the mil light. It could still have an issue , just not enough to illuminate the mil light.

I personally have never had a crank senser cause a rough idle issue.