: Regardless of who was in power of the military, the Covenant would fall apart
: or be destroyed when the rings were activated the the Great Journey was
: revealed to be false. It's not like the Brutes were just power hungry,
: they were also devout followers and believers.

Exactly.

So, if Truth knew everything was a lie, it's never really explained why he wants to activate the rings.

It's been suggested that he goes mad with power and gets to the point where he starts believing his own lies.

It never adds up.