Why is my phone not turning on?

I recently bought 2 iPhones. One was icloud locked and the other was stuck in recovery mode and wouldn't update due to error 4014. I swapped the logic board from phone which wasn't icloud locked and put it into the iPhone that was in the hope it was one of the connections that was preventing it from updating. Funnily enough it turned on first try and worked perfectly. The loud speaker was slightly muffled but that would be replaced soon. Before I got around to it I took a photo with the device and it just shut off despite the fact id taken photos with it prior. It was on 54% and there was no shut down circle in the centre of the screen. I’m to believe that this short circuited the motherboard but I’m not sure. Can anyone help on what needs replacing or what I should do. Thanks in advance.