iPhone wont turn on after display swap

I would take a step back and start by re-installing the original screen to see if the problem is consistent with the screen or the phone (logic board). I would also closely inspect the flex and connectors to insure there was no damage from the repair. Quick question - did you disconnect the battery prior to removing the display, and connect it only after the display was re-connected?

The other thing to try is to remove the screen altogether and connect the phone to an iTunes enabled computer to see if it is recognized. While you’re at it, you could also remove the RCAM and button flexes and keep the phone in a minimalist state.

My concern here is your cleaning process. In theory, distilled water in contains no minerals and is non conductive, so you’re approach to cleaning the device is sound. However, in practice, its possible that the “pure” water you used was not as pure as you thought or were led to believe.