The Fix has a theory:
Palin's involvement in the group will help rebut the idea that the National Council is an organ of the establishment wing of the party set up to keep the Palins and Gov. Mark Sanford's (S.C.) -- both of whom are more hardline conservatives -- from taking over control of the party.
Not entirely sure if Palin's a"hardline" conservative. At first she said she'd reject $416.6 million in stimulus funds; now $29 million.
Jerry Taylor, senior fellow at the Cato Institute and a leading conservative voice on energy, compared Palin's energy plan to something that would do Nancy Pelosi proud:
If you stripped the report of all references to Alaska, you would be hard-pressed to differentiate it from a report issued by, say, Nancy Pelosi’s office.
So her "hardline conservatism" is quite in doubt. It's hard to think of an area where she's more conservative than Bobby Jindal, Mitt Romney, or Eric Cantor, all of whom were leading figures from the start at NCNA.
So aside from her public image, it's hard to see why Palin would represent an ideological threat to the party.