FWIW every one of the machines you cited (“Sparc, old MIPS, old PPC, DEC Alpha, etc”) post dated the formation of the Internet (the arpanet transitioning to TCP); the Internet protocols just followed existing arpanet practice. Which was due to big-endian processors being common, but the dominant networked machine of that era was the PDP-10.
PDP-11 had a little endian architecture while big endian machines like the PDP-6/PDP-10 predominated on the net.
To make life more interesting, the later PDP-10/20 mainframes used PDP-11 minicomputers as front end processors and often as network processors so byte-swapping was the norm. Luckily the PDP-10 allowed bytes ranging from 1-36 bits wide - “byte” had not yet standardized on 8 bits
