Why does toast and butter keep me satiated

So I've been on a lot of diets. Keto. Intermittent fasting. Low fat. No carb. Carnivore. Cico. There's only one combo that'll keep me full and satisfied for hours. Two pieces of wheat toast and butter. Real butter. Not margarine. So I decided to investigate. Was it because of the fat? Fiber? But then I ate fiber with my broccoli. Toast and butter just hits different. I have PCOS so idek why this works. Once I realized it kept me full I tried to go on a high fat diet again. Didn't work. Then I tried to do high fiber and that didn't really work either. The only tried and true thing that I have done has been better and toast. Does anybody have an idea why?