Congrats on the weight loss Pie!! 
I would think it would have something to do with a reduction in swelling in your feet and ankles, but that’s just a WAG.
Holy shit! That’s the most impressive weight loss I’ve ever heard of.
I’m late to this party!
When I was 18 years old, I weighed 320#. At 19, when I went to FSU (in August), I had dropped to 300#. By 4 July of the next year, I weighed 180#.
My waist went from 46" to 34". My neck size went from 19" to 14". My shoe size went from 16EEE to 14EE.
I was all kinds of sloppy looking because nothing fit anymore. I used a strip of cloth to hold my pants up because the belt was nearly 1.5 times what I needed and was uncomfortable, even with new holes poked into it. My sneakers looked like I was auditioning for a spot as a clown at the FSU circus.
Thankfully, my Mom went to one of those cheapie stores and bought me a bunch of stuff stamped “IRREGULAR” and sent it to me. I wore that stuff for a year, and I felt like a king even tho the legs of pants were slightly different lengths and stuff.
So yes, when you lose significant amounts of weight, everything changes.
I lost forty pounds, but I still wear a size 8 shoe. However, I did have to have one of my rings re-sized (it was a bit big, then when I lost the weight it got really loose.) I might have to get my wedding ring resized too. I was rooting around in my purse and the next thing I knew the rings were dangling off near my fingernail.
A lot depends on how much weight you have on your body and how your body carries weight. Some people also tend to retain water more and have more edema problems with their feet when they are heavier.
I am trying to loose weight right now, but I would be shocked if my shoe size changed with the weight loss. I have more than 50 pounds to loose but there is no extra fat on my feet. I have a vein that sticks up on top of my foot even. It would be nice to be out of wides but I wear wide because of the structure of the bones in my feet so I’ll be in wides for my whole life.