Good investment decision and obviously the street was very wrong, but the reason the multiple was low was because of concerns earnings were at risk from a) their issues in China (which they solved, at least for now, but was a very valid concern at the time) and b) android eating them (there was a narrative they were about to be blackberried, or that android was doing what windows did to mac). There are good reasons why that didn't happen.
IIRC, tech in general was trading at very low multiples 10 years ago. Microsoft was also ~ 10, and Google and Facebook were probably < 20 as well.