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.
I'll just assume what you're trying to say is that everyone is trading with the US and so has plenty of money in order to fund stuff. If it wasn't the US, some other country would be the one with all the money. i.e. it used to be Rome. it used to be the UK. Even so, it has little to do with the US and purely the strength of your economy etc. Lots of people these days love to point to Venezuela and it's failure. But really, those in charge were morons and put all their eggs in one basket. They viewed oil prices in the same way wall street viewed the housing bubble leading up to 2008. Saying their socialism proves it's a failure when they were inept is just foolish.
Side note, the US is "mostly" capitalistic. You might be surprised to see who ranks #1 in terms of the most capitalistic. The USA is 18th. Note how many countries that are more capitalistic then the US, also have more socialism.
https://www.thebalance.com/capitalism-characteristics-examples-pros-cons-3305588