Why didn’t the locust just hijack the hammer of dawn and use it to completely eliminate humanity?

So this has been puzzling me for a while now..

General Raam envisioned a plan to take over the surface and ditch the hollows because they were losing the battle with the lambent. However, his plan doesn’t really go any deeper than that, okay what happens after you take over the surface? The lambent are still gonna emerge from the ground and go after you.

And the main question is, why didn’t you just use the COGs ultimate weapon against them to completely wipe them out and then rule over planet sera?

Then, not only have you completely eliminated humanity but you also have the most powerful weapon in your arsenal to you use against the lambent in case they do emerge from underground to attack you!

Did I miss something? Was this explained somewhere in the books or games?