Yes - iphone came out 2007 and Nokia was still the leading mobile phone company by sales in 2010, and Symbian had the largest OS share to 2012.
In my view it was really the two big OS decisions they made - first in 2010 they ditched Symbian to focus on 'Meego' (a partnership with Intel) then in 2012 they ditched all of that for Windows Phone.
Through those 2 years they moved outright owning the globally most popular OS to being the secondary manufacturer for the third best supported OS. And not trusted by users to provide any continuity.