If there's anything Christian about this poem, it's this line. The meek and weak human is a hallmark of Christian doctrine. To paraphrase: we're weak and God is almighty and powerful.
The Truth's superb surprise (4)
This reminds us of a religious epiphany. It's kind of like seeing the light, really understanding what it's all about.
The Truth must dazzle gradually (7)
We can't help it. When we see bright lights in literature we think religion, particularly Christianity, where God=light.
Or every man be blind—(8)
This line recalls the meek and mild part of Christianity. Mere mortals can't really handle the power of God. We're dazzled by his brilliance and power, so we've got to bow our heads (in respect, in prayer) if we want to be among that kind of awesome light.