The short answer
A deal riding on one person is not a deal, it is a favour. Gong's data is blunt about this: winning deals average around eight contacts on email versus three in losing ones, and deals between 50,000 and 250,000 dollars typically touch at least ten stakeholders. The move is not to email the CIO behind your champion's back, it is to ask your champion who else feels this problem and offer to do the work of bringing them in. Ghostwrite the invite for them, run a session framed around the problem rather than your product, and let the other functions add their own cost of doing nothing. Bring an executive in around the third touch, not the first, because starting at the top actually lowers win rates.