Yes, I'd like to know that too. If they're out for destruction, why this method on this world?

[So many other approaches would be swifter, if they've identified this world as a problem.

Right now, it looks more like they've created a problem]

What concerns me is that we don't see anything like the mining efforts in our last mission. I can't say I have the best gauge of their usual approach, but this...it seem strange.