I could go on and on, but you guys are missing the point- the least maneuverable vessel has the right of way in a confined channel. It could have been a sailboat under sail instead of a big cruiser, or a big commercial vessel- same rule applies.
Get out of the way.
It was wrong for "thousands of boats" to be traveling at "less than idle speed"- taking up the entire channel- more or less chatting and sightseeing, by the OP's own description.
You're making the assumption that the "big boats"-diesel or not- just "felt" like going faster than the "crowd".
I'm making the assumption that they needed to- to maintain adequate control of their boats.
Pay particular attention to the part below that says "avoid impeding the safe passage of a vessel...navigating a narrow channel" USCG regs.
5. Who has the "right of way" on the water? The Navigation Rules convey a right-of-way only in one particular circumstance: to power-driven vessels proceeding downbound with a following current in narrow channels or fairways of the Great Lakes , Western Rivers, or other waters specified by regulation (Inland Rule 9(a)(ii)). Otherwise, power-driven vessels are to keep out of the way (Rule 18) and either give-way (Rule 16) or stand-on (Rule 17) to vessels not under command or restricted in their ability to maneuver, sailing vessels or vessels engaged in fishing, and, similarly vessels should avoid impeding the safe passage of a vessel constrained by her draft (Rule 18(d)), navigating a narrow channel (Rule 9) or traffic separation scheme (Rule 10). The Rules do not grant privileges they impose responsibilities and require precaution under all conditions and circumstances; no Rule exonerates any vessel from the consequences of neglect (Rule 2). Neglect, among other things, could be not maintaining a proper look-out (Rule 5), use of improper speed (Rule 6), not taking the appropriate actions to determine and avoid collision (Rule 7 & 8) or completely ignoring your responsibilities under the Rules.
RR- to answer your question, too many people take the "no wake" designation literally. It does NOT mean the vessel cannot leave a wake. If a boat's moving, it leaves a wake...
It means the minimum speed required for the vessel to maintain steerage and make headway. For some boats, that might be 8 knots.