Why is did my phone die and not turn back on?

Unless the phone was severely dropped just prior to the failure, the phone probably just succumbed to water-related issues. When water gets in a phone, it usually works it's way onto the logic board and often times underneath the IC's, where there are tiny solder balls connecting the IC to the board. As the water evaporates, it leaves behind mineral deposits which can cause shorts. These shorts can make power lines fail (a dead phone for example) or bridge together digital logic signals (think erratic behavior).

At any rate, it's surprising that the phone worked for as long as it did. You could try to have decontaminate the logic board in IPA but it will probably still require some board level troubleshooting and repair.