Who knows? Google doesn't want to frustrate cryptocurrency. It's either they have plans that will give them advantage by having this decision. There's no reason why they did this but this also beneficial to the newbies who are just searching about "bitcoin / crypto" on google and after pressing the search button, those scams crypto ads appears. They will be now safe from those through the search engine but its still their choice if they will follow their own decision and thinking that they can be rich overnight through crypto.