I agree that it always seemed unlikely. The issue I've been trying to grapple with is this..

If it is possible for 51% of the network to be controlled by a small number of individuals, would it make any sense to even carry out the attack. I presume such miners would be carrying a large amount of valuable bitcoin, and any attempt to undermine the value wouldn't make sense.

The other side of the argument is that cartel style organisations are able to afford the vast expense to mine nowadays. If they can do that, is it feasible that they may orchestrate a 51% attack?

The glimmer of light is, that only a few organisations could achieve it, so they would be holding a smoking gun.

Interesting..