The poem's first line makes a blunt claim: business is a "holy urge." Money-making gets the language of religious calling, and the next line, "no thought or weakness," suggests what that calling demands. Doubt and conscience are not allowed. The speaker seems to be describing the mindset of the crusaders of the title, who act with total certainty.
Then the violence arrives. "Our guns went all off" is a strangely casual phrase, as if the shooting just happened, with nobody quite deciding it. The "our" implicates the speaker, so this reads less like an outside accusation and more like a grim confession or a flat report. In the final image, fire spreads "from church to church," and the bonfires are "made of prayer." Faith itself becomes fuel.
The mood is cold and ironic. The short lines and plain wording give it the tone of someone stating terrible things without comment. Judging by the imagery, the poem suggests that when profit and holy purpose merge, they destroy the very things they claim to serve.