The title tells us what the poem plans to do: illustrate the speaker’s vision of a quality of God, namely "grandeur." Grandeur is the quality of being "grand," which means "big," "fancy," "wonderful," or "splendid."
The seeming simplicity of the title does suggest that the poet isn’t interested in "selling" the poem, or giving it a snappy title to try to lure people into reading it. Nope. We have a simple statement of the focus of the poem. Enter if you wish.