Then you weren't paying attention to, well, the entire show and Londo's arc. Politics matters greatly to the Centauri. If the Emperor loses his political capital, AT BEST his underlings will use that lack to do the things they want done -- and that benefit them -- rather than what HE wants done. At worst, you end up with what happened to Cartagia.
That they don't implies that they were, indeed, aware that it could be done, at least in that case. And the episode strongly strongly implies that it is their special connection that allows for it, not that they are simply that powerful. Doesn't it flat-out mention that they train together specially for that?Still, you'd think someone could have taken like ten seconds to say ''wow, telepathic contact over lots of light years...I did not know that was possible."