The bubble bursts
Definition 1 of 2
Pro Tip 1/3False Stability
Used when a seemingly stable situation is actually precarious and collapses. 
Investors felt secure until the bubble burst, revealing the company was in debt.
Pro Tip 2/3Impending Doom
Implies that the end of a good phase is expected and inevitable. 
Everyone knew the bubble would burst the moment interest rates climbed.
Pro Tip 3/3Market Context
Often used in financial contexts to describe a market crash following a boom. 
The tech industry thrived until the bubble burst, erasing millions in value.