Every episode has its weaknesses. You've pointed out just a few among many in "Return of the Archons". This is not one of my favorite episodes, because of the sheer ridiculousness of it all. No, to make it more believable, people would have had something inserted into their cerebral cortex that allows Landru to control them. The only other alternative would be a massive amount of brainwashing, whereby with some specific cues (audible or subsonic), one could be kept in a specific frame of mind, and altered periodically (like for the "festival"). But oddly, the Enterprise landing party detected no such emanations.
The "hollow tube" absorption doesn't work thoroughly on everybody. Sulu was one of those weaker minded people who was affected. Hilarious how Landru's computer being taken down would suddenly free Sulu of his "grip"... up in ORBIT! ROFLMAO. See, this is one of those utterly ridiculous aspects of this episode. Anyway, Kirk and Spock were deemed more devious and willful, thus requiring the more elaborate absorption laboratory which would do a more thorough job. That's about the only thing I could thing of to try rescuing the inconsistency. Yeah, Sulu could've made a run for it, but apparently where he stood were the beam down coordinates. We didn't see him or O'Neil use communicators, which was puzzling. Also, the Landru minions move very slowly. As we saw, Kirk was able to yank one of those tubes from them with ease. Why wouldn't Sulu with his well trained physicality be able to do the same? STUPID.