When I was a kid I wet the bed. I think my mom was too cheap to buy diapers/pull-ups because instead she sewed extra pieces of fabric into regular underwear. They were uncomfortable and barely worked. I have lots of memories waking up in a cold, wet uncomfortable bed and struggling to fall back asleep.
Then, around age 5, I started wearing goodnites. This was because my mom signed up for a market research study so the diapers were provided for free. I was angry at first, but quickly grew to love them. A wet diaper was so much more comfortable than a wet bed. Each week was a different pack with different "formulas" or levels of thickness. Some weeks were VERY thick. Much thicker than goodnites today. They were all plain white and very much seemed like real diapers. There wasn't a sexual element yet, but I remember feeling a naughty sense of enjoyment. There was something thrilling about "going back in diapers" and feeling the bulky weight of my wet diaper as I walked down the hall in the morning, or sat on the couch and watched TV.
Now here's the kicker... as part of this market research study, my mom had to weigh each diaper, bag them and return them to the company. On top of that, I would have to sit down for an interview with a friendly middle-aged lady and answer questions about how each diaper felt, their level of comfort, tendency to sag, etc. My therapist highly suspected this was what cemented my fetish, as I was being specifically asked to think about the sensation of a wet diaper against my penis at FIVE years old.
I stopped wetting the bed maybe 1 year after, but pretty quickly started thinking about them. I had what I know realize was crippling anxiety, spurred by religion and the fear of going to hell. Anytime I was reprimanded by a teacher, even for something tiny, I would spend days afterwards with a heightened heart rate, unable to sleep. Somewhere I realized that the thought of wearing diapers was soothing. Whenever I was in trouble, or felt like I was going to be, I daydreamed that I could be put back in diapers. It wasn't about regression, but rather, in my screwed up logic, being shamed in diapers seemed like an adequate punishment that would restore the moral equilibrium.
Fortunately I've more or less cured my anxiety since then, but my appetite for being shamed and/or shaming others in diapers has marched on.