If he wants to stay in the first place why did he act like a child

Ego got the better of him maybe. Or my theory is he just wanted to put pressure on the owners to sack Slot.

Spot on. I think he was being told that the fans will support him over Slot. They obviously do not understand Liverpool supporters. Not too different from Trent's inner circle telling him, " You will be legend at Liverpool and RM! what could go wrong?"