Can we talk about trebuchets? Trebuchets are all anyone really cares about

Can we talk about trebuchets? Trebuchets are all anyone really cares about, we just haven't discovered this yet for some reason.

My main question is can trebuchets really bring down a castle? Probably not, but how effective were they?

You want the trebuchet to just erode the walls enough for you to climb through the wall right? So you set up the trebuchet, and you launch it at the same point in a wall, or castle, 20 times. Or is 2,000 times you need to launch that rock at that point? So how long exactly does it take to create some sort of entry in a wall?

How many times was this done? 2, 3? 100 times? Was it standard practice? And then once a bunch of heavy rocks have hit the wall, and knocked some rumble down, do you just send in some army up the rubble onto the wall, then inside? Or do you destroy multiple areas of the wall for multiple access points?

Or on second thought, are these trebuchet projectiles knocking out large parts of the wall? Doing serious damage? I can't imagine how. Anyway,