Groupthink happens because humans are tribal by nature. Tribes provide protection as long as you comply with their principles. Doing something contrarian is que

Groupthink happens because humans are tribal by nature. Tribes provide protection as long as you comply with their principles. Doing something contrarian is questioning those principles which is a threat to the tribe. Groupthink keeps you from being ostracized from the group as long as you go along with it because it’s desirable to be accepted in that tribe in order to achieve your long-term plans.