: So I asked myself why anyone would want The Mantle in the first place. The
: Mantle is power. Power over all species in an effort to protect them. The
: Precursors say that The Mantle can only be given, not claimed.. Remember
: that old adage? Anyone who desires power does not deserve to have it? I
: paraphrase, but there's the rub. Only those who have no wish to rule truly
: deserve it. So I guess the better question is...why does the galaxy need a
: species to hold The Mantle at all?

This is not true, the belief behind the Mantle doesn't actually state that the Mantle is to be upheld violently or through expressions of power. That was the Forerunner's bastardization of its core tenants of being peaceful caretakers for the races of the galaxy, and it's a large part of what led their society to fall.

It's like religious extremists claiming they need to kill for God, when there's nothing in religious texts that says violence will solve the world's problems. Same sort of situation.