Not surprising at all. Stopping cholesterol drugs while keeping lifestyle changes still lets numbers drift upward. The placebo participants probably noticed the return of hunger signals and the small justifications for extra snacks.
A study put obese adults through 36 weeks of the medication plus a 500-calorie daily deficit and at least 150 minutes of weekly activity. They were then split, with one arm switched to placebo for another 52 weeks. Even though the lifestyle program continued, 82.5 percent of the placebo group regained at least a quarter of their lost weight inside a year, and the earlier improvements in waist size, blood pressure, blood sugar, and lipids moved back toward baseline in step with the regain. The weight curves split clearly after week 36.