“Experts usually mean well, but they often don’t dwell in the world of reality.”
And the expert doesn’t usually have a long term relationship with the entity they are “helping” with advice. That means that they are likely ill-equiped to handle long-term, systemic issues such as delayed consequences.
But, that’s the consultant game, more so with the less reputable consultants. A consultant is less likely to want to create a sustainable situation because that means the consultant can’t come back in a few weeks or months for another hit. But even when this isn’t intentionally done by the consultant, the chances are that an organization will become over-reliant on consulting, on the outsider.
Sustainability should be a big part of the conversation between any organization and consultants they hire.