He may have betrayed the American left by giving propaganda ammunition to the American right. Is he partisan? I don't really know but I suspect. Why did he go to Russia, of all places?

"Russia first received information about Snowden when he was in Hong Kong. At that time, they were told that a person who wanted to fight against human rights violations wanted to seek asylum in Russia. In 2017, during The Putin Interviews with the director Oliver Stone, the Russian president Vladimir Putin described how Russia became involved in the Snowden saga. Russia did not want to get involved because of its strained relationship with the United States which it did not wish to worsen. Thereafter they learned that Snowden was on a plane bound for Moscow, to transfer to another plane bound for Latin America. Most of this information was received through informal channels including information leaked to the press. While he was aboard the plane, his destination countries grew reluctant to allow him in, and Snowden was thus stuck in the transit area of Moscow Sheremetyevo International Airport. While in the airport, U.S. authorities asked Russia to extradite Snowden. However, this was not possible as Russia had proposed a treaty on cooperation in legal matters, requiring mutual extradition of criminals, which the U.S. had not agreed upon. Further, the United States had never extradited any Russian criminal who had taken asylum in the US, hence Snowden's extradition would have been unprecedented. Snowden had not committed a crime as per Russian law."[3] https://en.wikipedia.org/wiki/Edward_Snowden_asylum_in_Russia

Snowden didn't have many options while on the run ... I think it's more interesting that he was able to stay away from the wide-reaching claws of the US, instead that he somehow betrayed a political trend.