Why is the car not starting but cranking?

Sounds like an immobilizer issue, but not guaranteed.

Immobilizer is a security device which only allows registered key/keyfob to start vehicle, normally by controlling fuel supply to engine.

When immobilizer was triggered, you can only crank, but cannot start the engine.

However, I strongly recommend you go get a mechanic to diagnose your car properly, eliminate all other possible causes first, like you said, fuel/spark/air, etc.

Personally, I would not just jump straight to immobilizer, cause it should not be triggered if you did not do anything wrong.

There are more things which may stop the engine from starting/running, fuel/spark/air are just basics, you should also consider about timing and compression, immobilizer should be the last thing to check.