IMO it's a chicken and the egg thing, they probably got some quality early users(similar to what Quora did) and those brought in more quality content users, soo

IMO it's a chicken and the egg thing, they probably got some quality early users(similar to what Quora did) and those brought in more quality content users, soon enough more people were getting in just because that's where the knowledge exchange for tech people is, even if it's not the best tool for the job itself.