People react to a crisis when they often don’t if it’s just an everyday problem. For example, a major international airport might have been begging for more money for security and for years been held back by the accounting department. Suddenly, there is evidence of an imminent terrorism threat. Now there is a crisis.
Most people are familiar with the term “ambush” and know that it is a surprise attack that is designed to catch the adversary unaware (even if they are expecting it) thus rendering them more vulnerable.
A poisoned chalice is something that seems good at first (a beautiful cup filled with delectable wine) but after the person accepts the cup and drinks from it he or she discovers that it is poisoned.