After gallbladder surgery, up to 10% of people experience Post-Cholecystectomy Syndrome. Bile, which is made in the liver and normally stored in the gallbladder, now gets dumped directly into the small intestine (see Diagrams — Gastrointestinal Anatomy). Since bile may be heavily concentrated, it pulls in water to dilute it (an imperative of physics), hence the diarrheal stools. If it’s going to occur, it tends to begin soon after surgery, not years later.
Post-Cholecystectomy Syndrome is harmless, but may be disliked by those who have it. The medicine cholestyramine may help, but causes a variety of mild but unpleasant effects which may be perceived as worse than the diarrhea. We could gradually build up to the highest dose tolerated; but since the syndrome may eventually go away on its own, we might have to stop & start a few times to figure it out.