ClassicRyder, truly sorry to hear of your loss and certainly have every reason to believe the loss was something mechanical. But accidents are complex and conditions both of the bike, environment and traffic among them, and of course the rider being a major part of a motorcycles' dynamic performance and maintenance is key in solo or two up conditions.
This is why they have whole teams of analysts pour over an airplane or train when tragedy happens. The statistics on most modes of transportation says there are 1,000's of satisfied users verses not, just as there are possible thousands of reasons for a motorcycle to develop a wobble, much less specifically that would cause an accident.
The classic one is tire condition as the tires not only help to induce wobble, but are like a shock absorber dampening it by virtue of the tread pattern and profile. Another is steering head bearing preload (no play), fall away, and chassis attitude and suspension setup. Again, a very tough call and certainly real enough to always check your ride for your specific cause and effect and get it fixed promptly.