So the back story is that it is trivial to set up a "fake news" site and slant the crap out of the news and outright lie about what is going on to attract that segment of the population that is more interested in having their views validated than they are in learning anything new. And if you do that and fill it with aggressive ads you can make enough money per month to buy beer easily and sometimes even fund a comfortable lifestyle in a country which has a low cost of living.
So Google is going to stop selling ads to those sites. (good move on their part although it does impact their bottom line slightly) and they are going to stop taking money from those sites which try to buy adwords and make their site appear in the search results for a popular keyword. Also good but somewhat problematic.
This is the problem. Google sells ads on bids, highest bidder gets the best ad spot. Search ads are their cash cow and lifeblood. Hackers and fake news sites compete with each other trying to buy the ads on searches that hapless people do trying to find information about current events. So Google profits both by selling adwords and by the competition all these bad actors are engaged in trying to buy that top slot. Stop selling them adwords or stop allowing them to bid, and Google takes a big hit in topline revenue. How much remains to be seen, but if its a problem I expect fake news to be a hot topic at Searchengineland.