The Soviets, for military and security reasons, were closely monitoring the Apollo program at a point when the US and USSR were locked into the arms race and the Cold War, and the prestige of being the first to the Moon and back was enormous. Had the Apollo program been faked in even the slightest way, the Russians would have jumped on it and exposed the fraud for the world's media, to embarrass the US at a time when bogged down in a long, unpopular war in Vietnam; the Soviets would have so loved that! The Soviets reluctantly accepted they had lost the race to the Moon.
Then, there were 6 more successful lunar missions, and also the "successful failure" of Apollo XIII, until the program was abandoned some 2 years later. We would have had to pull the wool over the Soviets' eyes in 7 consecutive, incredibly expensive fakes. The Russians remained mute.
Yes, the Apollo landings did happen, of that there is no doubt. And best wishes and happy 40th Anniversary to all who participated in this wonderful pioneering and peaceful adventure.