Well for the Republican party to have chosen a course deliberately to avoid winning, there would have to be a chance for them to win in the first place - or say, some rising star they'd prefer to keep off center-stage that they ended up running a screen for or something.
The field was pretty week, their electorate was not really enamoured with any of the frontrunners, I'm not really aware of anyone who wasn't in the race who could have put together a winning campaign.
I'm just not sure I buy the plausibility of the premise. I don't think we need to ascribe that kind of shrewdness to them to explain their decision. After all, Palin does have an undeniable appeal. Especially at first, it likely seemed like she was exactly that kind of "rising star" I mentioned above. And they put her center stage, instead of saving her for 2012, because they thought they could win with her.
Hindsight, and the spectacular gaffes and obvious intellectual defecits make it seem like: "woah, why the hell did they pick her? Did they want to lose?"
I'm pretty sure the answer is: "well, it seemed like a pretty good idea at the time"
We should also remember that McCain of '08 had lost much of the lustre he had in his insurgency campaign of 2000. Another question might be: would a different running mate, even a really strong one, have made any appreciable difference to the outcome?