Second-hand? We have a fucking video. The people who were there wrote fucking books. We have the fucking capsule they returned in. We took souveniers. There's a flag on the surface of the moon. If that's second-hand, what do you count as first-hand? Do you need to be physically on the moon before you admit we went there?
It's not that the soviets had no reason to. It's that they had EVERY reason to, and didn't. They could win the space race and break public trust in the USA with one good piece of evidence, so long as that evidence existed. If there was any actual proof that it was fake, the soviets would have done everything possible to find it.
You honestly expect me to believe that:
The USA created a fake video of the moon that could pass for real in the 1960s;
They were able to stick a flag upright into the moon without manually positioning it;
They were able to synthesise a moon rock that could pass for real in the 1960s, when studying that rock progressed our science significantly;
They could create rockets, shuttles and capsules capable of taking people to the moon that we can see today in museums, complete with blueprints, and didn't use them;
They were able to cover up this secret so well that every engineer, scientist, set designer, cinematographer and government official kept the secret for 55 years;
They were able to do this 6 more times in the next 4 years;
Not one shred of evidence of any of this has been found, despite spies and sceptics looking for half a century;
...All while the president can't fuck a secretary without people finding out? That seems less likely than the US being able to go to a moon in that moon rocket they built.