This tactic goes back to those ancient times when heroes didn't have the Wisdom skill, and even the most primitive computer tormented the enemy army with disposable hero-kamikazes wielding Armageddon!:smile13:
Well, that's right! If you analyze everything in detail, it's difficult to pinpoint which aspect makes the computer play better.
Although, I've noticed a trend that with each new installment, the computer becomes smarter but less dangerous. This is true because the developers are improving the AI engine and fixing bugs.
So, in my opinion, the computer has become smarter at playing. For example, in the first part, it could capture a Castle but not build anything or deploy any troops for defense. In the second part, it constantly split its forces, which was the key to "defeating the computer in parts." But in the third part, that's over. However, in the first part, Armageddons and Storms were used by everyone, and that was annoying.
Conclusion: The older the installment, the more dangerous the computer is, and the newer it is, the smarter it plays.