Consumers are not savvy as a group. There is always an "eternal september", new suckers born every minute, that can be abused. Beyond that, there are plenty of ways that you can maintain consumer trust while abusing it at the same time. You can sell them products that hurt them in ways they don't understand, and you can control the media surrounding your product enough to ensure that they don't understand. Advertising has a basic purpose of making people aware of products, but it also serves to mislead them on the value of things, overstating the benefits and understating the costs.
This idea that people understand the total consequence of what they do with their money is so simplistic that it's stupid. Markets don't "speak" from a vaccuum, they demand what their constituents are convinced is valuable, regardless of the accuracy of valuation. Lies sell garbage all the time and the consumer isn't to blame for wanting it, the professional, skilled, psychology-wielding liars who sold them on it are.
Hypothetical example: pay for a bunk study that concludes eating apples prevents hair loss, benefit for decades, with negligible repercussions to your business when the lie is uncovered. I'd be skeptical if you claim you can't identify several real examples yourself.