Not sure I agree. I think that he desperately wants to be Prime Minister. But I honestly believe he has rightly assessed that his only viable path to doing so is to "hang in there" and try and keep his coalition from falling apart until the burden of governance leaves the other guy unpopular enough for PP to win by default- and he's going to do everything in his power to help the bolded along regardless of honestly, principles, or actually beneficially influencing policy.
The risk reward on a pivot doesn't line up. It's way too hard a needle to thread to win people over, and is just about the only thing that could cost him his bomb proof cult of support.
Why make a big bold swing when you can keep your ears pinned undermining the other guy while collecting 300k, an expense account, and Stornoway?