Not sure what you mean by market share and profit share. It seems a bit confusing...
Look back 5 years, smartphones were blackberries, treo etc. The iPhone came along and it people actually wanted it so it took over the market. But you need to remember that they dominated the smart phone market, not the whole mobile phone market. Now, 5 years later, you practically can't get mobile phone that's not classified as a "smartphone".
Bottom line, practically all of the mobile industry is now classified in this smartphone braket so their market share lowers. But Apple's market share isn't the whole smartphone market, they only care about the high-end stuff. They'll sell you one of their old iPhone model but that's not really their gig. They only care about the high end stuff because that's where the money's at.
They get the customers that don't mind the higher profit margin but expect innovation, they get the customers that will actually spend money in the App store, they get the customers that change their phone every two years and it's much easier to market the best. Lastly, the competition is done over desirability and innovation rather than on how cheap they can ship.
So if you look at what Apple sets out to do, sell expensive phones, their winning. Other than lately the Nexus 4 (which I have doubts about the profits it generates to LG and Google), I don't see much competitors with traction.
I think the competition in both the mobile and computer market is way off. In the mobile market all I see are ugly plastic phones with ugly not useable UI. In the computer market, most of what were seeing are copycat product stuck on Windows.
ps: I'm switching from an iPhone to a Nexus 4.
