If I were guessing I might say that maybe this is happening:
Right now the more trade China has with Iran the more America might make a fuss. Either complaining politically, putting tariffs, or calling on general favours and good will for it to stop. But if America starts making a fuss anyway, or burns all its good will, then their is suddenly no downside to trading with Iran. Now substitute “China” for any and all countries (for example the UK, France and Germany, who all stayed in the Iran Nuclear Deal even after the USA pulled out).
That Iran thing is weird.
If I were guessing I might say that maybe this is happening:
Right now the more trade China has with Iran the more America might make a fuss. Either complaining politically, putting tariffs, or calling on general favours and good will for it to stop. But if America starts making a fuss anyway, or burns all its good will, then their is suddenly no downside to trading with Iran. Now substitute “China” for any and all countries (for example the UK, France and Germany, who all stayed in the Iran Nuclear Deal even after the USA pulled out).