Why did Impressionism cause controversy?

Impressionism was considered revolutionary because the European Academies of the mid to late 19th century were still training artists in the Academic style which depicted landscapes and people in a realist style. The French Impressionists chose a more relaxed style with thicker paint (impasto) and a brighter pallet. The result was more distinct and artistic as opposed to the mundane repetitious images being pumped out by Academic artists.