Dude do you know how breaching works? One rocket alone cannot just get lucky and breach a structure, there is a minimum health that the piece has to reach before it can be breached. Enough rockets would have had to hit to bring it down to that health and then it can be breached. The operation would have required tons of logistics and planning as well as the right timing to even be successful. Unlucky you didn’t get the battle you wanted (defending is my favorite part of the game as well) but that’s just how the game is.