Earlier quoted context omitted.
I mean that's what you get for using PNGs for pictures.
It's not the format but the image size. For example: https://l3ouu4n9.github.io/2021/note/BHUSA/1.png - 37 megapixel - 50MB.
This image could have been scaled down from it's current dimensions of 9894x3786 down to say 1920x210, and it would still probably contain basically the same amount of information really.