What you just described is the reason the USA refused to join the League of Nations and broadly viewed as one of the reasons the League of Nations failed. FDRs "4 policemen" (which evolved into the P5 vetoes on the UN security council) was intended to address that issue. The UN has arguably failed too in that regard (although we also haven't had another world war so perhaps it depends on what you view as its purpose).
But more importantly in this case, the UN has grown enormously beyond its original setup and taken on many other functions. This has led to corruption and worse, the ability for bad actors to put a veil of legitimacy over their intentions and actions. It seems to that that is what has happened here. Unfortunately it's all too common with the UN.