Toddler sleeping problem

My toddler turns 2 in December and I just had a baby 7 weeks ago. And when I was pregnant my son would go to sleep without a problem. Now he will throw the biggest tantrum screaming and yelling and crying the whole 9 yards. He just wants to play if he can stay up till 1 am he certainly would. When we put him in bed he will just scream to go down then we put him back into bed and he will just be crying and then out of knowhere he will just stop crying and stair at me or space out and will just be silent and then he starts to slowly fall asleep sitting up… is that normal? He is FULL of energy all day long so I’m surprised he doesn’t want to knock out early and easily.