system
Given the following post, respond as if you're commenting on Reddit:
human
[Rick and Morty] Regarding S1E06 'Rick Potion No. 9"

Towards the end of the episode when Rick is explaining to Morty how there are infinite timelines, he says "It's not like we can do this every week, anyways. We get three or four more of these, tops". My question is, if there are "infinite timelines" why are there only finite universes where certain events happen?

EDIT:Thanks for all the helpful responses! Watched a couple of YouTube videos and I am grasping the concept now.
gpt
Of the infinite universes, there were a finite (though a vast amount) number of them where Rick cured the infection in time for the world to return to normal.  Of those uncountable worlds where Rick solved the crisis, there were also a finite, but smaller amount than the first, where Rick and Morty died soon after due to whatever.  If Rick and Morty manage to doom their current world, they are cutting their possible future escape worlds down further.  

Infinite universes do exist, but there are only a finite number of them where Rick and Morty could conceivably insert themselves into. Think of it as when Rick was trying to find a planet for them to live on after becoming fugitives.  Out of the millions of places they could have went to, only three planets were livable.  While there are infinite universes, when you start applying filters to them and cut them down exponentially the numbers get small real quick.

Also keep in mind of the original worlds where Rick cured the infection, and then died soon after, they were reasonably similar to his original world.  I.E.  they don't have giant telepathic spider problems, they all don't look like Rocky Dennis from Mask.  So Cowboy Rick and Morty could also destroy their whole planet, but they would be limited to the infinite universes where Cowboy Rick and Morty exist to escape to.