At first, not many made the connection, but as time goes people began suspecting that there was something between those two but what stopped them from really doubting Alex was the fact that it was not an open secret that Alexander and Leonardo never get along, so it was nigh impossible for the two to cooperate, especially when Leonardo was one of the culprits behind his sister kidnapping back then, but the emperor knew the truth.
He knew that they existed a deal between Alex and Leonardo; as for what kind of deal it was, he could easily tell, but he could infer, whether his inference was true or not, he didn't know.