The car cranks and cranks but wont run?

The brake pedal is stiff because the vacuum from the booster is gone and that is normal. Once the engine starts the pedal will return to normal.

The engine not starting is most likely a weak battery or a fuel issue.

So, we need to start with checking the battery. Here is a guide that will show how to do this:

https://www.2carpros.com/articles/car-battery-load-test

If the battery is okay, then we need to monitor the fuel pressure when this is not starting.

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

I don't think messing with the battery caused it to start unless there was a loose connection but instead after the battery sat for a short time, it is able to regenerate some power and it would start the vehicle.

However, if the battery is fine, then I suspect that was just a coincidence which means we should see the fuel pressure low as that is the next likely issue.

Let's start with this info and let us know what you find. Thanks