zanzibar: Yes, poor play is sadly deserved if only for 4...e5? .
Such a move shouldn't be played against a player of Tal's caliber.
Why not? Well, simply because Black is already behind in development, and putting the pawn on e5 allows White to develop with tempo.
And 5...exd4 opens the e-file - and we see what happens with that when the king is stuck in the center.
In fact, this is the idea - White sacs a pawn for a huge lead in development, and the opportunity to catch the king in the center.
So - Black made a poor move with 4...e5 and is essentially losing by 6.Bc4. Playing 6...Nf6? just plays into White's hands - opening lines, removing a defender and exposing the queen.
Of course, since I have an engine, I see that Tal missed a chance to get a minor piece out with with 8.Bg5, the best move for that position. Perhaps Tal knew this, and actually was setting a trap.
To avoid the trap, Black would need to be aware of the danger remaining after 8.O-O, and play the defensive move 8...h6 (which doesn't help Black catch up with White's development).
Trying to protect the pawn with 8...Bc5 loses the game. Look at the position after 8.O-O:
Black is already lost - not so easy for me to see, but it's true.
An extremely instructive opening to study - at least, it was for me.