The first commercially successful arcade video game was Pong in 1972. According to https://en.wikipedia.org/wiki/Arcade_video_game the number of units eventually sold was about 19,000. (A lower figure of 8,500 is also listed, but looking at the references linked from that page, that seems to be only the number sold in one year.)
A subsequent game, Tank, is said to have sold over 15,000 units in total: https://www.wikiwand.com/en/Tank_(video_game)
Those numbers look surprising when matched against recollections of the time. Pong was iconic; it was everywhere. Tank was... well, sure, it existed, it was reasonably popular in its day, but I had forgotten its existence until I looked it up; it certainly doesn't seem to have had anything like the iconic omnipresence of Pong. How does that square with the estimates of the two games selling roughly equal numbers?
One way to square the numbers is to note that both are specifically for the Atari versions. But Pong was very heavily cloned. In those days, patents didn't start applying until granted, and it took two or three years from application to grant; for that reason, Atari did not put the application at the top of its initial to-do list; this is discussed further at https://en.wikipedia.org/wiki/Pong
So maybe the Pong clones make up the general ubiquity that game seems to have had.
But that leads to another question: why did the same thing not happen with Tank? Why was the world not similarly flooded with Tank clones?
Tank, being more complex, was harder to clone. But that doesn't really make sense; the reason they were able to make it more complex, was that the technology had moved forward, and it had also moved forward for the cloners.
It was indeed similarly cloned. But that doesn't square with the obscurity of that game relative to Pong.
Atari was quicker to file a patent for it. But the 2 to 3 years delay in granting the patent, should have left time for clones to appear.
Atari had become better at manufacturing, and was more capable of quickly supplying the market, leaving less unfilled demand for the cloners. I suspect that might be part of the explanation.
The industry was waking up to the fact that video games could be about other things than bats and balls. That led to companies pursuing a variety of different designs, so that a smaller percentage of the total effort went into cloning Atari's latest game. I suspect that might also be part of the explanation.
But there might also be other factors that I haven't thought of.