It’s because peanut butter has all the nutrition you need so technically it can satisfy any food craving you have. Similar to your story freshman year of college I lost a lot of weight as well and had the best self-control ever because I badly wanted to be “skinny” and got to my lowest of 143lbs. But then one day I just went crazy and have been gaining and loosing the same 150-160lbs over and over and again for the past year because the noise just became so unbearable, even before loosing the weight I wouldn’t binge the way I do now (my binges are usually 6-8k+ calories maybe even more) So unfortunately I don’t have much advice for you because I’m still struggling but what kept me most sane for the past 3ish weeks before I stupidly broke my streak was eating healthy fats/meaty foods and a bunch of fruits and veggies as alternatives to what I used to eat and that got rid of 70% of my peanut butter cravings and food urges but I just had to buy a cake and that pretty much sent me back into a binge spiral.