Why did Ng Man Tat throw grenades and blow them up for export?

I think there should be a mistake. Uncle should want to close the road, but it's like the principle of washing your feet before you thirst for water when you see a lake. It doesn't make sense. Why do I say that? He had been escorted out because of the students, but at that moment, the big uncle dropped his glasses. Before that, he was very arrogant, like a terminator. From this point on, all the essence of sand sculpture was exposed? First, the enemy chased him for glasses, and then he threw a Grenade at the hole. After the explosion, if the uncle wanted to be selfless, he wouldn't go into the hole again, and then he went out and said that the export exploded. I think he may have a brain cramp and reversed the order. The normal order should be to throw a Grenade in the direction of the enemy to block the road into the hole, and he also has a Grenade. It's not too late to blow up when you get out of the hole. All in all, this is a nonsense performance, so I doubt that glasses are noumenon. It can also be said that it paved the way for being caught later, and compared with A Xing's later professional appearance, it showed the toughness of the number one killer of the Flying Tigers, insinuating that the so-called tiger of serious crimes was not professional enough except pretending to kiss up.