Reason I support the Dubs is I visited San Francisco and LA in the summer of 2009. Fell in love with San Francisco, LA not so much. Decided to support their baseball team (San Francisco Giants).
Next year (Summer of 2010) I visited family in Vancouver who got me into ice hockey. Naturally, I decided to start following the San Jose Sharks (As they're the San Francisco Bay Area ice hockey team).
I then got slightly bored with ice hockey and so decided to branch out to the other sports in the US. Didn't actually follow the NBA for another couple of years, with 2012/13 season being my first for it and so again, I chose the team from the Bay Area, so Golden State. NFL came last, first season being the 2014 season. So naturally I followed and chose the 49ers.
So that's the roundabout way I ended up with Golden State.