Why is the left pushing the idea of socialism/comunism so much even tho it showed that it doesn't work many times in the past?
They're not. It's the extreme left that is pushing for a lot more socialism and it's only the extreme radical left that might say communism but I rarely see that sort of thing. As for it not working? There are plenty of countries where more socialism is working just fine for them so the argument about it not working is false. I'm curious though. Which countries do you think work without having any socialism at all?
Except that socialism is working fine in the narrow view. The wide view shows that socialism success is based on relations with capitalistic USA.