Roy Smith wrote
Are you trying to tell me that a jump plane released jumpers out of
sight of land and with no navigation other than a radar controller
telling them where they were???

Yes, that is exactly what happened. That particular incident is quite
famous in the history of skydiving. In fact, back when I instructed,
that was the incident that we used to underscore the importance of not
exiting the airplane if you can't see the ground. The sport has since
changed, and exiting without seeing the ground is once again
relatively common (if not generally legal) - but now it's done with
GPS guidance. Eventually some pilot will incorrectly program or
interpret the GPS and this will happen again.

Also, 105.17*says, "No person may conduct a parachute operation [...]
(a) Into or through a cloud". Was that regulation (or something
similar) not in effect at that time?

That regulation is quite commonly broken even today, though this may
have been prior to the existence of Part 105.

Michael