My question is can they bid on it behind the scenes like a keyword. Siri suggestions must have some type of revenue.

It would be a poorly considered algorithm rather than some bidding situation. No sane person would build this intentionally. The big companies have too much to lose especially.

Basically, this is Google's entire business: getting paid to send us where someone else wants us to go. Google are "big". Why wouldn't Apple want in on this action?

Sponsored search results are marked as such in the Google results, it's nothing like the automagic redirect Safari is showing here.

Apple uses this to promote first party services like Apple Music, Apple News, and App Store. All of these generate revenue for Apple.

If they land on Google, then Google would be promoting YouTube Music, Google News, etc, which is lost revenue for Apple.