US government believed he was trying to get out of Russia enough to ask 3 countries to close their airspace and ground the Bolivian president's plane to search it. But hey, feel free to keep living in denial.
The US government "believing something enough" to take a small chance is no evidence it is true or that it had been Snowden's intention to be on such a plane.
All the arguments I've heard so far against the possibility of Snowden having been recruited before the affair assume Snowden is telling the truth. Which is not sufficient in my view.