I may be overly optimistic, but I believe that as individuals almost everyone would help if they knew someone was in trouble. But I can think of multiple reasons people might not help in a situation like this. I suspect the main reason is in these crowded spots there's some of that group dynamic thing going on: assume someone more qualified or experienced will help out, so you don't need to. This would be particularly true for visitors: feel unconfident in local knowledge, the guy down is local pro, surely one of the other local pros will take care of it, etc. Sometimes there's the fear of personal risk: if I just barely feel in control of my own kite/board in the circumstances, how am I going to help someone else?
But more specific here: from what you said you were fairly far out and a little off the main track. My guess is most people did not see you crash and once down you are pretty much invisible. Anyone who did see you either didn't understand the potential or probably assumed you would self-rescue (and the worst possibility: that "serves you right" mentality, as in "you got yourself into that spot, so you can have the long swim as a lesson", not realizing you are hurt).
This last one prompted some self-reflection by me and our crew in a local incident. Our spot often has sketchy winds, we regularly push it and downwind self-rescues are often the norm, sometimes more than once a session. It starts to get routine, especially with relatively new riders, to the point that no one bothers to check -- assume it's just another routine self rescue. Except when it isn't: buddy wrapped in his lines, getting dunked and half drowning. A tourist waded into the surf zone in our cold water to save him, meanwhile me and his buddies are standing around 500m upwind BS'ing. No one had any idea. The new personal rule: if less than 100% certainty, do not assume -- check and be sure. I don't want to face the fact of a friend or visitor dying while I could have helped. Complacency kills.
Another realization that came out of it: you can't do the universal help sign of waving your arms if your arms are wrapped or you are fighting to stay alive. And without that arm wave, a semi drowning from a distance looks the same as a normal self rescue. We had a group meeting to talk it out and implemented a safety protocol in our crew to carry marine safety whistles, wear it on a lanyard near neck level. If in trouble, clench it in your teeth and blow the crap out of it while using your arms to free yourself or otherwise save your life ... more chance of someone hearing it and alerting the crew. But that was 2-3 years ago, no incidents since, complacency set in, pretty sure no one wears them any more ... along with no helmets, impact vests, etc. Would be interesting to do a check one day of how many people at the beach have functioning line cutters. Safety preparedness seems lame and kooky 99.9% of the time, then that 1 in 1000 day you need it, it's not there.
So ... maybe you should host a locals safety meeting, to talk about your experience, hash out the "what if's", refresh the group's commitment to safety, and also emphasize personal responsibilities (safety preparedness, expectations when kiting solo). Hashing this out as a group may help. BBQ up some food and play a stoking video to add some fun, spoonful of sugar for the medicine.