Tulip bulbs were one of the first derivative traded items. This was because the bulbs were seasonal and therefore a futures market was established which meant that the "bulbs" were traded without a physical exchange of goods; effectively it was a paper contract to buy (or sell) the bulbs when they were in season. The lack of physical exchange made the trading easier and therefore was more susceptible to rapid swings in price (rapid being relative for the 1600s).
Without the benefit of history, it is easy to see how speculators got carried away as values continued to rise, assuming that greater returns would follow. Only when the market ran out of buyers did the realisation quickly set in the price collapsed to virtually nothing in one single day.