The tide turned
Definition 1 of 1
Pro Tip 1/3Unexpected Change
Use 'the tide turned' to describe an unexpected shift in events or circumstances. 
The court case seemed decided until the tide turned with a surprising witness testimony.
Pro Tip 2/3Metaphorical Tide
Remember, there's no actual water involved; it's a metaphor for change in fortune or events. 
With the tide turned, the small business began to thrive.
Pro Tip 3/3Sports Commentary
Often used in sports to describe a game-changing moment or momentum shift. 
After half-time, the tide turned and the underdogs took the lead.