These people's deaths may not have been linked to the "fit for work" findings (although one might think that the heightened anxiety arising from the pressure to find work and potential or actual benefit cuts would be bound to worsen some health conditions). What matters more, I feel, is that they were assessed as "fit" when their deaths shortly after the assessments would suggest otherwise.
Of course, without a proper analysis (e.g statistically, during the same period, how many working people not subject to the assessment process die unexpectedly?) it is difficult to form definite conclusions. Personally, though, I think more and more evidence is stacking up to suggest that the assessment procedure contains major flaws and cannot be relied upon to identify who is or isn't fit for work.