Well, King/Tsar/PM Simeon has achieved a tremendous amount on his own- both being a very successful business leader AND becoming Prime Minister by popular will. Wouldn't that give him a lot of satisfaction?
Plus he's still royalty and gets to hobnob with other monarchs. As he was only a kid when the monarchy was abolished, perhaps he doesn't have as many bitter memories as King Michael of Romania would have?
That said, I do not know much about King/Tsar/PM Simeon, but hopefully a highly accomplished life due to his own capabilities gives him a lot of satisfaction.