That's one of the approaches indeed. I think it has merit, since trade relations create dependency, and dependency can be leveraged to enact change in the other

That's one of the approaches indeed. I think it has merit, since trade relations create dependency, and dependency can be leveraged to enact change in the other's behavior. At the end of the day though, politics is complex, and it's also tied to the people who participate in it. So while many people can suffer as result of a systemic change, the people who brought that to action might have different incentives, might not had the foresight, might have weighed the pros and cons and calculated with it, might sacrifice short-term good for a longer good... might be corrupt even. TL;DR it's complicated, and it probably has an official, and a real reason as well.