"All in all the entire event still does not make a lot of sense"
SLF here. Perhaps it didn't go 'according to plan' and the bizarre disappearance we now have was unintended.
Most deliberate actions are a consequence of trying to attain a premeditated goal. If that includes long-planned suicide (or the remainder of one's life as an international criminal) by persons intelligent and informed enough to carry out this act, I fail to believe that they would throw away their lives lightly. I think they thought they had a decent chance of success, and as Occam's Razor tells us, the simplest plans with the least dependencies are the most likely to work.
It might be helpful to try to figure out what was intended, in the most basic way:
* An influential public statement, like 9/11?
Once its perpetrators had decided to act unconstrained by behavioural norms the 9/11 plan itself was quite simple and straightforward, with few dependencies. Even so, it only partly succeeded. As a public statement, so far MH370 seems to have a pretty obscure purpose, whereas 9/11 was clear and comprehensible.
* A disappearance intended to precipitate an insurance payout?
MH370 seems so far to be an unnecessarily complicated way of going about it. There have been plenty of prior instances and I'd expect an intelligent perpetrator to try to avoid their complexities, weaknesses and failures.
* An attempted theft of the airframe, its cargo, or passengers?
Sure, but once you have them, what are you going to do with them? Again, if the overall plan is complex with many dependencies its chances of success are low. As has been pointed out before it's probably easier to seize the cargo before flight. It's probably easier to kidnap individual passengers before flight. And what are they going to do with this particular airframe which couldn't be done with another? I'd have thought it would be far easier to seize a freighter or bizjet on the day if the goal was to drop a dirty bomb on a city or disrupt The Hague talks.