when you do factory reset sometime it takes longer time to startup need about 5 minutes and don't interrupt the process or you can stuck in bootloop if that happen try flashing your phone.

check you internal storage not microsd nor external storage, best solution will be free your internal storage space by delete any junk files or clear your browsing cache

be careful when charging battery in wet condition it can burnout your phone. as far as i know the battery can be very quickly drained because the chemical insdide is not working at its optimal such as short at terminal postive and negative this can be happen because there is water trapped inside battery. best solution you can dry your battery using hair dryer or you can dry by expose it to the sun light until fully dry.

1st try flash with new rom if it doesn't work my best guess is the lcd defect or just need replacement

did you insert the touch screen flexible correctly?

how you done the factory reset by the way, might be the OS data corrupt or bad memory module. you can try flash with new rom

are you sure that you insert lcd flexible correctly? i have also experienced same prob and fix it by replace mainboard

could be lcd module or hardware problem, when the phone off does lcd turn on when charging?