If you’ve ever spent much time around a small child who is old enough to walk, from about age 2 to 4 or 5, you know you have to keep your eye on them all the time because they are impulsive and heedless. They will run off in any direction at the slightest inducement, potentially into the street if the mood strikes them.
Donald Trump is the toddler president. He impulsively chases whatever shiny object happens to catch his eye, heedless of the harm he may cause. Given that the shiny objects he notices now are public policy choices, he can harm millions of people. Worse still, his instincts to please the largest possible crowd at all times leads him to choose the worst, most harmful possible policies, like building a useless, wasteful wall at the border or banning people from entering the country because of their religion, unless they come from a country he does business with.
Having a toddler as president is a really bad idea. We should take steps to avoid ever having it happen again.