That's how he 'negotiates'. He bullies his opponent then throws a toddler tantrum when they stand up to his demands. When they back down he makes a new demand.

He does it because IT WORKS. Every time he he throws himself on the floor and kicks his legs someone backs down and teaches him that it's an effective way to negotiate. Every single person who has backed down to him is responsible for teaching him. And then they're surprised when he does it again.

Anyone familiar with early childhood development can tell you why it's a bad idea to give in to a baby like him. But no world leaders, apparently.