Display worked for 2 hours after Speaker repair and then gave up

You say you replaced the speakers what was the issue with them? Probably unrelated but interesting to know. In terms of what caused them to fail originally could potentially be causing the screen to fail now.

The left speaker was defective. It sounded all distorted and crackly. It actually wasn't the first time I did the repair. Replaced the speakers about 5 years ago for the first time.

My initial thought is you bent a display ribbon too far . Then you say it’s not displaying via HDMI. I’m thinking a board issue. I could be well wrong just a hunch. Hopefully someone more knowledgeable on Macs and iOS steps in .

When you replaced the speakers, did you have to remove the logic board? I just replaced a crackly right speaker in a 15" 2012 MBP, and found a way to do it without having to remove the board. But if you removed the board to replace the speaker, and if the video connector cable looks fine, my concern is that the logic board was damaged during replacement. You may not be able to fix this without replacing the board. One thing I might try would be to disconnect the internal display, and re-test the HDMI video. Another thing to look at is heat, since your MBP worked for a few hours before failing. There's even a 1% chance your Mac was about to fail anyway, and that replacing the speaker was unrelated.

Yes I had to remove the logic board. Not sure how to do it without removing it, because one of the screws of each speaker is right under it. I'm going to try your suggestion with disconnecting the internal display.