US CBP (predecessor) pre-clearance arrangements came into being initially at the request of US airlines. The reason Canada and the US went for these kind of CBP PreClearance agreements/arrangements was to further commercial integration of the Canada-US passenger airline networks and to try to make things more convenient for commercial airline passengers and expand the route network and the economic viability of service.

This latest US government push for the CBP preclearance arrangements at (non-Irish) European airports is driven by something else (namely, security paranoia), and these arrangements if implemented at (non-Irish) European airline hubs will slow things down for way more people and result in passengers spending more time in lines (and less time being able to stay in the premium passenger lounges during transits outside of the US on trips to the US).