At the time it was not clear that GLP-1 solves obesity problem so effectively - many drugs suppress hunger (eg amphetamines), it's just that GLP-1 works long term and does not have significant side effects. Hard to predict without hindsight.

Insulin is injectable so GLP-1 was thought to be at best marginal improvement over already existing protocol - so likely profitable product but not excessively so. Company has limited resources so decisions on cuts have to be made and some of those decisions are naturally wrong - drugs are unpredictable.

On regret - they missed on 30B+ of profits so of cause they regret it.