Trusteeships (and later colonies) were a net drain on the economy of the home countries.
Similar to, although considerably less so, the way we've made a profit by invading Iraq and stealing their oil.
BTW, this is the time period during which the US was pressuring the colonizers to pull out, resulting in almost complete decolonization during the later 50s and 60s.
The US (I assume that’s what you meant be “we”) stole Iraq’s oil? How so?