I'm not sure, but such an act requires a lot of planning and resources, I rather doubt that it was merely retribution without some more complex rationale.
Trying to keep an open mind about it.
The Muslim world has long had to fight Western exploitation and insult, these days much of it has to do with resources, all of it coupled with centuries of grief over religious differences.
I agree with you about the obscenity of the cartoons and how that might have put it over the top.
The publisher was able to run more successful campaigns with less vulgar depictions.