Well a nonzero (and possibly quite large) number of those are bots. OSRS is a fun game but it's design makes it very easy to make bots for. If you play for a while you'll see them almost everywhere.
https://gitlab.com/mtekman/runescape-motiondetector
It worked for about an hour before having the nasty habit of attacking monsters, chasing them out into the wilderness where you'd check in on your character and find him dead, barren, and lost.
Fun though.
Its almost a cool emergent ecosystem, except it sucks for us real players.