I doubt that the configuration has anything at all to do with the accident rate, but the mission (long hours hovering OGE close to obstructions) is certainly a difficult one.
I don't know why the synchropter config was not used for the later Kaman airfraft designs, which were naval shipboard aircraft ostensibly well suited to the syncropter design. If we are saying that Charlie Kaman dropped the syncropter from his bag of tricks, does that mean Dave must add him to Dave's private list of "Designers who don't know what a GOOD helicopter looks like"?