So how do you explain the scepter and crown solution?
IMO: The scepter and crown solution is a perfect meeting of good players and good DM'ing. The players are engaged with the game and the setting, and they are ready to think laterally to solve their predicament. The DM is willing to "say yes" and allow an inventive solution to work. It's a great moment.
Of course, if the players are going through the module as part of an ongoing campaign (as opposed to a one-off at a tournament) the trick will get old in a hurry if they keep trying it. Such is life.
The scepter and crown solution was also (IIRC) an on the spot ruling made by Gygax at the request of the referee who was running the module. I'm not sure I would say that the crown and scepter PC's "figured out which arbitrary idea Gary had in mind," but I think it is fair to say that they won by appealing to Gygax's discretion. I also think that Gygax's exercise of discretion was to some extent "arbitrary." He could have reached any number of different rulings if he had cared to.
Which is consistent with the rest of the module. We've seen a number of encounters in the Tomb that could play very differently depending on how the DM handled them -- the timing of the Agitated Chamber, and the precise way the Juggernaut works are the first examples that come to mind.
I hope to sit down and organize my thoughts this weekend, but I'll get a little ahead of myself here. I don't think the Tomb of Horrors gives the players anything like a "walkthrough". I don't think it is possible to get through the Tomb simply by reasoning through Acererak's clues.
On the other hand, I think a group of cautious players can minimize most of the worst risks in the Tomb with a few fairly straightforward tactics. (Most significantly, by sending an expendable scout ahead of the main group.) A group that makes liberal use of magic and rests frequently should be able to make it to Area 33 without a TPK.