Because they've had multiple years and billions of dollars to build out their infrastructure. They got crushed during the Super Bowl and had a very clear example of what they needed to fix. An inability to handle traffic isn't a mistake, it's a strategic failure. There's an important distinction there.
Additionally, you should be more critical of the institutions that make billions of dollars off your money. This isn't a small local business deserving our patience and understanding. It's a $50b company acting as the financial backbone for digital currency.