I don't think this needs to be seen as a monopoly move. Think of it instead like health inspections for restaurants.
In theory, restaurateurs would hate health inspections, because they're intrusive regulation with no direct benefit. But they have a lot of indirect benefit, in that the safer people feel going to restaurants, the more likely they are to go out to eat.
Similarly, the safer the web is, the better off Google is, because people do more things on the web. That does benefit them, sure, but I don't think it benefits them disproportionately, let alone harms other legitimate competitors.
In theory, restaurateurs would hate health inspections, because they're intrusive regulation with no direct benefit. But they have a lot of indirect benefit, in that the safer people feel going to restaurants, the more likely they are to go out to eat.
Similarly, the safer the web is, the better off Google is, because people do more things on the web. That does benefit them, sure, but I don't think it benefits them disproportionately, let alone harms other legitimate competitors.