Basically, his party got beaten so badly at the European elections (barely got half of the far-right votes, and almost got the third position after the Socialist), that he decided to trigger a “Dissolution”, which literally stop the current assembly mandate and call for flash-election. His gamble was to make himself the only alternative to the far-right by counting on the left division and the fear of the far right…
Which blown up to his face since the left kinda united itself and the far right still got a good advance. Even worse, this time its party got third by a long shot, and may loose a lot of its seats at the National Assembly.