I think I understand it. It makes sense if his goals were to 1) release this information and 2) survive afterwards. Doing #1 was relatively easy, as he had the access to accomplish it.
But to then stay alive and (relatively) free required being beyond the reach of the US government. Being in the States is out of the question, and by extension so is being in any country with an extradition treaty with the US. I don’t know what all the options were, but ultimately he chose Russia as the place he would live.
If you assume his goal is freedom for mankind in general, it does seem hypocritical to go running to an authoritarian country for safety. But it seems pretty clear he wasn’t motivated by a vague principle, but rather wanting to blow the whistle on a specific injustice he saw.