So ‘success’ = not falling behind. Okidokee.
Can you really say that sensors increased profit, any more than say reducing personnel or manufacturing expenses?
Incidentally, two of the drivers of market share are brand loyalty/familiarity and popularity. I have Brand X so I’ll buy another one of them when the time comes. Particularly true when accessories (e.g. lenses) help lock in users. Plus if my friends use it, maybe I should too. Point being, barring a paradigm shift (Sony sensors aren’t, nor is removing the mirror from an ILC) or a manufacturer truly screwing things up, market share shifts slowly. Sony was (and remains) 3rd, well ahead of Fuji/Pentax/etc. They didn’t need great sensors to maintain that lead over Fuji/Pentax.
If a better sensor actually had the impact on the market that you seem to think it does, Sony would have gained some market share over time, as would Nikon for putting Sony sensors in their bodies. Instead, Sony stagnated and Nikon lost while Canon (without ‘great sensors’) gained.