Because, in the previous turn, he was standing near the mine and had a whole turn to think and decide. He could have gone through that passage, taken the city across the sands, played it safer, or gone with his main hero. He could have pushed my hero. But the fact is, he checked his hero near my main hero, which turned out not to be the case, so he wouldn't attack if he were there, and he covered it, judging by his logic, which is what he thought. But as Dima Surmai said, the risk didn't pay off. Everything turned out differently: