It wasn’t the dow, but ALL the economic factors that are up. ALL OF THEM. The stock market is succeptible to ‘irrational exuberance’ and ‘animal impulse’. So the market overreacts in both up and down directions as it expands and contracts.

The market was overheated because speculation that the trump tax plan would have beneficial effects, drove up the prices. Now that they’re here, some people are taking profits because they can foresee a correction.