This is 100% true. It's much more obvious in the novels, because Earth is trashed to mass extinction levels, and it's pointed out much more explicitly that the Belt is not self-sufficient and that all humans will ultimately die without access to Earth. To a large extent, Ineros is motivated by the same understanding that Mars has - with the habitable worlds through the ring gates, the Belt about to become 100% irrelevant. No one will even want to buy their shit any longer because they'll just go to a virgin planet and mine it there. It's a desperate plan to knock back planet-bound humanity while there's still somewhat of a chance and to stop the flow of settlers to new worlds. It's not really a good plan. But that doesn't matter, because a man with a good plan has been manipulating him.