Press and hold "D" key after you power on the mac to load Apple Diagnostics. Alternatively if you can connect to internet, press and hold "Option" + "D" key at the same time to load Apple Hardware Test.
when you hold the option key, did you see the arrow pointer but do not show any disks? If no means your keyboard maybe faulty. you can try both the left and right option key one at a time and see if you get a response. if not use an external apple usb keyboard. take note that MacBook air boot up time is quite quick so you must be holding the option key already when you press the power button otherwise you will lose that window to enter boot option menu.
1. Ensure logic board is completely dried up. Use hair blower with low temp setting if needed. 2. If above did not work, buy a keyboard replacement and see if it can trigger the power. Liquid spills can easily kill a keyboard. And power button is integrated in the keyboard circuit.