Could be a few things if it but the first thing I might do is plug it into a computer and see if it is recognized, it could still be a screen fault even if there is only the preexisting small crack and no visible damage. It can be hard to know if these devices are powered on depending on some device settings.[br]
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But more likely in my opinion, the drop or whatever caused the back glass to shatter may have caused something on the board to come loose, crack or become otherwise damaged. Especially if it was hot and then got no power, that sounds like a short on the logic board. It’s possible to repair that, but you would need to get it into the hands of someone who can do microsoldering.