If you are fasting for weight loss, you might try something less extreme like OMAD. Nobody here can tell you why you fainted, but 3 days fasted is definitely a deep fasted state. It is not necessary to fast that long to lose weight. Just eat a heathy, relatively low carb dinner, and fast the rest of the time. You’ll lose ~2 lbs a week, which is at the upper end of what is considered healthy weight loss. It’ll be a piece of cake compared to rolling 72s!
Many people (me included) actually like eating OMAD. I lost my weight in 6 months but continued to eat in this schedule ever since (3.5 years so far) because I like not being bombarded with food all the time. My body works better just eating once a day.
TL;DR, if you fainted doing an extreme version of IF, consider a less extreme version like OMAD.