what does "crushed" and "killer comedy bit"mean iin this conversation?
it's from a talk show where two comedians are talking about Donald Trump.
-he is a stand up comedian. he works the material, he grows it , he goes out there, and then you can tell when it's starting to get old, you feel the crowd sort of like ,"yeah, yeah, new jokes."
-yeah, it is true, like, because "build the wall", I feel like that was just a bit that crushed, and then , now he realizes he has to build a wall, and it was just a killer comedy bit.
-well, can you imagine if we had to do the things we said in our jokes. I mean, I would be like, "I don't want to be a comedian anymore"

Question

what does "crushed" and "killer comedy bit"mean iin this conversation?
it's from a talk show where two comedians are talking about Donald Trump. 
-he is a stand up comedian. he works the material, he grows it , he goes out there, and then you can tell when it's starting to get old, you feel  the crowd sort of like ,"yeah, yeah, new jokes."
-yeah, it is true, like, because "build the wall", I feel like that was just a bit that crushed, and then , now he realizes he has to build a wall, and it was just a killer comedy bit.
-well, can you imagine if we had to do the things we said in our jokes. I mean, I would be like, "I don't want to be a comedian anymore"

Answer

If this case when you "crush" something means you did a really good job at it. That joke "crushed" meaning that joke was really popular. Another example "Oh i crushed my final exam at school!" I did really well on it.  For the killer comedy bit also kind of means the same like it was really well. He did a killer job. He did an amazing job. Another example "Oh he's a really good chef, he makes a killer cheeseburger!"  Hope this helps!