Oelm
Auto-translated
Perhaps the AI believes that since victory will be its own, it can play with minimizing losses. In a single-turn analysis, the arrows clearly don't pose a threat, so it eliminates the single units so they don't counterattack the griffins (it's interesting whether it takes into account that it takes 2 attacks to counterattack). Once the archers are protected, it has nothing left to do but attack the covering stacks.