Tactics for the Stronghold.

Of course, it's because of the tactics. And his wolf ability doesn't interest me at all. It's the combination of attack and tactics, and the rapid increase in attack power as the game progresses.
imo

Even if that's the case, just for your information: the attack increase of upgraded wolves is greater than the attack increase of birds.
However, they need to be played VERY skillfully.
And they are very sensitive to the morale of neutral creatures.