"Toddlers want independence and control over their environment — more than they can actually handle. This can lead to power struggles as a child thinks 'I can do it myself' or 'I want it, give it to me.' When kids discover that they can't do it and can't have everything they want, they may have a tantrum."

https://kidshealth.org/en/parents/tantrums.html

In this case, Trump wanted the whole country as his toy, and he's now basically saying "If I can't play with my toy, then no one can!"