Dave's a naturally quiet, decent guy to begin with; Weider was looking for someone with a more outgoing persona to elevate BB when he brought in Schwarzenegger. In the early 70s Dave sued Weider and won something like 20K in court but missed out on a likely payout in the millions by declining to go after Weider as he could have. That legal acrimony ended his relationship with Weider; after that he was barely seen elsewhere, other than occasional articles in 2nd rate BB mags like Lurie's, in the mid-70s.
Dave had serious problems with alcoholism in the 70s as well-he was supposed to be part of the Pumping Iron footage but wasn't all there when then film crew showed up at his house.
Things have been much better over the last 10-15 years with the gym ownerships (financed in part or in full by Schwarzenegger) and with this great site he runs, which includes his line of equipment and supplements as well as good articles on training and BB's past. He continues to make custom wood furniture, something he's done for decades.