Why crop before anything else
Cropping removes pixels outright, which makes it the most effective single change you can make to an image's file size and its impact. Cutting away empty sky, a distracting background, or the margins of a scanned document reduces the weight of the file and pulls attention to the part that actually matters.
Because cropping happens before compression in a sensible workflow, everything you remove is weight you never have to compress. Crop first, resize second, compress last, and you will consistently reach smaller files at higher visible quality than by compressing alone.