A few minutes research reveals that the budget for the first two films was $115,000,000. The films made $474,544,672 and $310, 675,583. That's a difference of $163,869,089 -- prompting Lucasfilms to drop the budget of the third movie to 113,000,000 in anticipation of a smaller return. The third movie did do better ($380,262,555) but still significantly less than the first.
People stopped spending their money on the films after the first. That's how bad it was.