Other commenters have gone over many of the reasons why Go got popular, and I don't claim to know for certain, but in my view one important one is probably Rob

Other commenters have gone over many of the reasons why Go got popular, and I don't claim to know for certain, but in my view one important one is probably Rob Pike. He obviously has a well-known pedigree, he's very articulate, and a lot of people latched on to his "Go philosophy". Combine that with the reputation for unrivaled engineering excellence that Google had in 2009 and it's not surprising that Go got as big as it did.