Either Apple will make their devices refuse to sign the attestation if you're using it, or Google will remove Apple from its list of trusted attesters.
Or (most likely) they will negotiate how to split the money. Maybe through some kind of safe advertising consortium.
Apple is just fine with collecting user data on platforms so long as they're the only ones doing it. Apple even runs its own ad network over its own app store.
If you ask anyone who works in advertising they always say Apple has by far the "worst" targeting options. They display ads in the App Store but the data they use to track is usually not very great.
