Lyle, sorry for your loss!
There is always the human factor! Distractions happen unfortunately.
I recently launched my boat right after watching a guy drop his boat off his trailer backing down ramp. He actually removed cable AND safety chain. We were in the middle of getting ready when this happened. My wife and both forgot to remove outdrive transport bracket until in the water with lots of people ready to launch or load. Laying on the swim step i blindly removed all three parts soaking my self to the neck.
Some will say you should have done a pull test. Test I agree but a "VISUAL" test would have done the same.
Your call but you should start a new topic on this to remind people to do the "TEST" of their choice!!!