Because it's not designed to be opened past 90º, (very few laptop models are so designed, none of them Apple) you've shorted, pulled, or broken the connections/cab
If this answer was helpful please remember to mark it accepted.
It sounds like you may have either a pinched cable, a broken cable, or a faulty display. I hope, for your sake, that it is only the cable that is pinched or disconnected.
Take a look at this guide to show you how to get the display cable out of the computer. iFixit also sells both the data cable and the LCD, if it comes to that. If it comes to replacing the display, follow this guide.
Since you say that the display turns off after a certain point, I suspect a faulty cable. For a start, check all the connections in the data cable, and inspect the cable for any tears or shorts. If the cable checks out, you may need to spring for a new LCD. Often the inverter boards on the back of these panels can go wonky after a few years, but this usually is usually demonstrated by the screen fading to white rather than black.
Replace your cracked, dark, or dead-pixel infested MacBook LCD. Compatible with all 13.3" MacBooks (excluding MacBook Unibody and MacBook Air). 1280x800 LCD / 13.3". Glossy and matte options. — 3 available at 149.95 each.
A damaged display data cable can cause video defects — 13 available at 39.95 each.