Number of factors: Obama is a minority and voting for a minority is like voting for a non-White.
Asian Hindu Indians are hostile to the GOP because they saw Bush being favorable to Pakistan and the rest of the GOP hostile to H1-Visas and increased immigration.
Asian Muslims see the GOP hostile because Bush decided to fight back against Muslim terrorists.
Other factors...anti-American/anti-White and anti-Israel feelings among many segments of Asians.
Not all. Several Indians I work with are very conservative. They state the reason they left India was to get away from socialism. They like Onamacare almost as much as I do!