The BBC quotes him as saying the old V8 rules had become "hard to explain" amid the trends for "downsizing" and fuel efficiency within the road car market.
Asked if Mercedes would have pulled out had the rules not changed, he admitted: "I think so, yeah. We had hard discussions."
Weber explained that the new rules now make it easy to "clearly convince" the decision-making board that F1 has become relevant and worth the investment.
He said recent statements that the rules are too complicated were "stupid", insisting that the quieter engines are simply the sound of the future.
"Of course we can look if there is a little bit more (volume) possible," said Weber.
"But in the meantime all the road cars are going for turbos, downsizing, so even a Porsche now sounds similar. So people learn it. That's easy."