system
Given the following post, respond as if you're commenting on Reddit:
human
[Fallout: New Vegas] How could the Bright Brotherhood possibly have failed to reach the moon and yet survived?

In the good ending, it is said that the ghoul cultists helped some civilians get away from the fighting during the final battle, obviously meaning that they survived their attempted voyage to the moon yet did not actually reach the moon.

From this, I personally like to surmise that they crashed but miraculously all survived, and Jason interpreted this as a sign that they should remain on Earth and work to improve their kind's relations with normal humans rather than fleeing from them, but the question still remains to speculate on regarding the circumstances, and location, etc., of their somehow non-fatal crash.
gpt
They may have had enough fuel to get into orbit, but not to escape Earth orbit and slingshot out to the moon. However, your theory that it was purely a leadership justification for an accident is more likely.