There was a lot of optimism when Ben Ali, Mubarak and Qaddafi were ousted, then a lot of disappointment. This study suggests we should not be surprised:
“since the end of the Cold War, regime change of some sort increasingly follows successful coups (68 percent pre-1990 compared with 90 percent afterward, with the rest simply reshuffling the leadership). Though more of these changes now end in democratization, the most common outcome is still the replacement of one dictatorship by a different group of autocrats …..56 percent during the Cold War and 50 percent since the end of it.”
“The bad news does not end there. Using annual data on repression, we find that coups that launch new dictatorships lead to higher levels of repression in the year that follows than existed in the year leading to the coup. Moreover, in daily event data for the 49 coup attempts that have occurred since 1989, we find that there is only one case of a coup followed by a drop in state-caused civilian deaths during the subsequent 12 months.”
https://www.washingtonpost.com/news/monkey-cage/wp/2016/02/22/are-coups-good-for-democracy/
IR Theory & Practice 