Circa 2010, Symbian was clearly uncompetitive and MeeGo was far behind schedule. There was a fairly ambitious plan to build a new UI framework in Qt that ran on both Symbian and MeeGo -- the Nokia N9 used this with Harmattan, which internally I don't think we ever referred to as MeeGo, IIRC! -- but I'm pretty sure when Elop arrived he took stock of things and thought, "My God, this MeeGo thing is Nokia's version of Apple's Copland project," and it's really hard to say he was wrong.
Looking back, it's really easy to say that he was wrong not to choose Android, but it was seriously considered. The problem was that Nokia insisted on two mutually exclusive conditions: they wanted to use a lot of Nokia-based services so the new devices still "felt Nokia," and they wanted to fully partner with Google and market the devices as Android. And Google wouldn't do it. If you want to call your device "Android (R)" then you use Google services; if you want to use your own, you have to do what Amazon did with the Fire devices. Google wouldn't make an exception for Nokia, but Microsoft -- who by that point had, at least internally, realized Windows Phone was seriously floundering -- would. And so they went with Microsoft.
They dawdled and ignored the problem for too long, and were left with selling to Microsoft and adopting their mobile OS as the only semi-plausible way to maintain a strong market position. Both Nokia and Microsoft's efforts ended up being too little, too late.
From the outset it looked (from the outside) exactly like his goal was as described - torpedo the company and get it bought by Microsoft, returning to the mothership in the process.
While I am absolutely pissed ( to say the least ) that Nokia was sold to Microsoft and Yahoo couldn't turn its ship around. I dont think both CEO were doing in their own interest or another companies interest.
Nokia refused to use Android. ( Which was what really killed Nokia ) That was only two possible outcome, either go full force with Symbian or partner with Microsoft. I mean there are so many wrong with Nokia even before Elop joined nothing much could have been done. It turns out the penalty for completely dismissing iPhone and Smartphone was death for their phone division. ( Currently the Nokia Smartphone are manufactured by a JV formed by former Nokia employees and Foxconn, with the name licensed from Nokia )
Elop did however completely neglect the importance of Carrier / Network Infrastructure segment, although arguably Ericsson wasn't competing much and Huawei didn't show up on their radar. ( Yet )
Marissa was trying very hard to recreate Google within Yahoo. She was absolutely executing it. But it is one of those example where I put the argument against execution eats strategy for breakfast.
It is not one OR the other. You need both. The equation times both together. When you have a strategy which trends towards zero or even negative, it doesn't matter how well you execute it.
In the end she failed. The strategy was wrong from the start. I actually thought the other CEO candidate's vision of turning Yahoo in to an Online Media Companies suits Yahoo better. But Marissa got the job, and the rest is history.