It’s not uncommon for HMRC to make sweetheart deals with large multinationals.

Yeah, but only if the deal means getting more money for HMRC.

If a company says “actually we’re going to declare our business operations in tax-free British Sark” then HMRC has to petition the government to stop them from doing that or risk getting no income at all

Or it can cut them a deal now. It’s a deal with the devil, but these are the realities of getting any income at all