That should be your first clue.
Ahh, the coverup theory!
I found plenty about Banks regarding his involvement in the disintegration of the Know-Nothing Party and about his Civil War record. Nobody seems to be interested in the period in-between.
Most northern and Republican officials either publicly denounced Brown without reservation or did that fancy dance about deploring his tactics regardless of how admirable his cause was.
If any officials openly proclaimed support for him, much less planned a military attack to rescue him, I’ve been unable to find it. If you have such evidence, I’d like to see it. There was kind of a panicked retreat from Brown on the part of northern supporters for a while. All but one of his financial backers, the Secret Six, chickened out and claimed to know nothing of his plans for violence.
Major weenies. The only one with balls wrote to one of the others (who had no balls), “Sanborn, is there no such thing as honor among confederates?... Can your clear moral sense justify holding one’s tongue…to save ourselves from all share in even the reprobation of society when the nobler man whom we have provoked on into the danger is the scapegoat of the reprobation-and the gallows too?”
Your post seems to imply that if there is no evidence something happened, it constitutes proof it did. Which is kind of silly.