what did i do wrong

8ts defo not damping off. Your stem has been pult by cave in in your sub and roots pull your stem/or you it can be a weak stem and excess stretching (top heavy) but I think it's what I have all the time. I explain. Bro.. all you have to do is brace that to stand up right. If you left it like that for 6hrs you'll find the leafs will turn straight towards the light. Try this 1st. Push soil one way and when you have the Stem straight. Then lightly compact the soil around it: this might keep it in place. If you still finding it falling over. It just a case of tie sub craving in and pulling roots 1 way that In turn pulls the stem side ways. So if that the 1st option does not work. Do what I did on King's banner. And a lot of my other plants. I get sub cave in all the time. So happens to me a lot. Can also happen with excess stretching. But yours looks just like a cave in. So you need to put a stick that runs the length of your stem. Lightly brace it with string or something. Just don't tie it tto tight to the stem as the roots will spread out and she'll be braced perfectly.. takes 3-5 days. Look at most of my grows as I always pack my sub loose to let my young seedlings get air ASAP as seedlings for it hard to breath as the soil stays wet for so long. Hence why I always get cave ins as sub is loose that o2 can get to roots. Good luck pal