"Any technology sufficiently advanced is indistinguishable from magic" - Arthur C Clarke
So, you're sitting way out in the solar system beyond our ability to see and you have this massive launcher capable of throwing rocks the size of a city. Just like a bowler, a skeet shooter, or even a baseball batter - but with much better technology, you toss one rock one way at one speed - you have to get it going first because it has a longer path to the target - then you toss another rock from a different direction at a different speed, and a third with a different trajectory, all designed to coincide at one point at the same time.
Hey, guess what, sports fans, the US Army already does this! It's called a Time On Target. It's a Field Artillery fire mission where every available gun shoots the same grid location so that the rounds hit at precisely the same time. The farthest guns have to shoot at one time and the closer ones a few seconds later, all so that the splash - the artillery rounds hitting the target and detonating - occurs simultaneously. Baaaad day for anyone in that grid square; your world just blows the f*ck up.
Extrapolating our ability to do that to a larger, galactic-energy, or possibly just a solar system-energy scale, even we could do it. Any civilization capable of traversing space to get to us likely also would have mastered the ability to control energies on a massive scale, far bigger than where we are, or even where we'll be much further down the road when we can control our planetary energy and make it do what we want it to.
On top of the mastery of enormous energy, one would have to have the patience to set these bodies in motion years before their scheduled rendezvous with their intended target, with attention to their trajectories that defies our ability to muster, currently.
Likely? I have no idea. Possible? Yep!
"When you have eliminated the impossible, whatever remains, however improbable, must be the truth" - Sherlock Holmes (Sir Arthur Conan Doyle)