Whether anything is a strategic blunder would require the length and breadth of history to evaluate correctly.
What has lost MSFT the battle in terms of current smartphones, could by virtue of the direction it has sent them in, end up winning them the war.
Mistakes, or benefits, are only such in terms of the specific standard they are being compared to - the specific output, much like the idea of "good" or "bad". In the end, what might be perceived as a strategic blunder, could either be the smartest move ever, in the long run, or some happy accidental fortune.
Or it might be a strategic blunder. But nothing is ever complete or a totality. All outcomes, all time, or all knowledge is never possessed.
Unless the sun goes out, and we are all dust, then perhaps, we can call it a totality. But then I am fairly sure no one will care about smartphones.