RE: How was that possible?
An ASI will still work with plugged static ports, but it will give inaccurate information. The DG and AI will still function as well. A plugged static port only affects the Airspeed indicator, Altimeter, and VSI. So a problem with a plugged static port would only readily be visible after takeoff, when the VSI and Altimeter fail to move after takeoff.
"As employees, pilots are a difficult lot. They are masters of their vessels, answerable to no one for as long as the engines are running. Airline presidents have the power to control entire fleets, to decide where and when every plane shall fly. But once those decisions are made, no one tells the pilot how, or even whether, to fly."
Commercial Pilot ASEL - Instrument Rated
Air Traffic Controller - Anchorage