> There isn't conclusive evidence of an absence of launch, ...

A launch is detectable seismically, visually, on radar, etc. There's a lot of investment in being able to detect launches (to detect the launch of nuclear weapons). It would be screamingly obvious if the launch was fake. It would absolutely be conclusive if there were no seismic activity, no radar return, they couldn't detect the spacecraft presently, etc. At least for a definition of "conclusive" that can be operationalized - conclusiveness is a judgement call about when evidence is sufficient and not reaching some theoretical 100% certainty. Which can't possibly be reached for any claim for the reason you outlined; you can always invent some negative counterclaim that can't be entirely dismissed, even for claims like "the sky is blue".

It's also pretty easy to find people who were physically there to witness the launch. This wasn't a secret bunker or a barge in the middle of the ocean. It was in Florida in the late afternoon.

> ...it would be accused as being fake and a ploy from American enemies to discredit them.

Hundreds of thousands of people around the world have access to this data. Astronomers, geologists, petroleum engineers, backyard amateurs. The conspirators could muddy the waters but they couldn't ultimately prevail. It is many orders of magnitude easier to go to the moon than to convincingly fake it.