What are the differences between Korea, Japan, Iran, and Saudi Arabia, even though they are all in Asia?

While Korea, Japan, Iran, and Saudi Arabia are all top contenders in Asia, even among these Asian national teams, there have been times when Japan stood out as the undisputed leader. It seems like there have been instances of a "1 dominant, 3 mid-tier" or a "1 dominant, 1 mid-tier (Korea), 2 weak" structure (including Asian Cup results), right?
Why is it that even among the same Asian national teams, they perform so differently in international matches?
In particular, watching Saudi Arabia and Iran from 2022 to 2026 has been so frustrating that I've even shouted out loud.
I thought, "If they were like Japan, if they had beaten Argentina in the first match, they would have likely secured a spot in the Round of 16 early with at least one win and one draw in the remaining matches," but Saudi Arabia felt somehow stifling...
And looking at Iran in 2026, I thought, "If it were Japan, they would have definitely reached at least the Round of 16," and so on..
What are the differences between these powerful Asian national teams?
Looking strictly at their overall strength, there doesn't seem to be much difference, yet they all produce different results when challenging for the next round in the World Cup.