As a Calif diving fan for the past 5 years, I can attest to the fact that kelp reaches out and grabs you like nothing I have ever seen! Especially at the surface. Most dive boats give a briefing explaining how to come up and avoid it - try to come up right at the steps, but if you come up away from boat you do the "kelp crawl" which is you stay on your belly and push down on the kelp as you make your way to boat. This is true all over Calif and really works! Diver may have come up away from boat and done like everyone does in other locations, rolled over on his back and tried to kick to the boat, thus entangling himself.
I Dive - yes, most divers do wear too much lead, but in Calif with 50-60 degree water and thick 7mm suits, it is necessary to wear more than you do in Fla. I personally like my integrated BC, but I see lots of wt belt divers in Calif. It says he was from AZ so it may be his first time in such heavy gear, too.
Do we know which dive boat he was diving from? It says 6 divers, but since it is the kelp beds right at SD, it could me any number of boats that normally hold more divers. Nowhere does it say a panga or inflatable boat. Some dive boats people hand up weights, but since article says he was tangled and fighting the DM, I doubt he took off his BC to hand it up. I think we need to hear from the dive boat guests and DM before we speculate what happened any further.