It is mainly to adapt their business to a new European law that is taking place as the months go by. Some businesses need to obtain a license from the financial markets authority in order to offer their service in the targeted country. It also allows them to advertise in these countries. That's why Google is also adapting its rules so that businesses can use google ads.
A concrete example with binance. Since it got a license in France, its services can be advertised. Advertising is not the main goal of this new law, it's just a point among others.
That's at least the reason for the European area. I don't know about others countries but it's surely mainly too to their recent changes in the local regulations (i.e. South Korea, UAB,...)
This change in google ads was planned in May, not a big change, it's rather a clarification. of
this and some crypto stuff still can't use the advertising platform. trading signals, affiliation, ICO, activities related to the purchase, holding or exchange, and so on...
Google has always been kinda strict as with crypto-related ads, right?
Not always, but for some years, yeah.