"That I understand, big publishers actually benefited from Google News being shut down in Spain."
No advertiser is going to think "hey I'll pay site x a load more money for advertising because although they have less viewers at least they get more than a very small site that no-one looks at anymore"
A news site isn't fighting for ad revenue amongst just the other news sites. They're fighting amongst every other site on the internet. Therefore an advertiser will want to see, number of impressions, quality of readership (/targetting) and number of click-throughs (or other such metrics).
Less traffic will just hit their advertising revenue. It's as straight forward as that.