The drone could have quickly left South Korea and returned to China after destroying the ground systems and being attacked by three South Korean warships firing anti-aircraft missiles. If Yan Fei had chosen to do so at that time, the events that followed wouldn't have happened.
However, Yan Fei didn't do that because he suddenly thought of something: it had been a long time since his drone's Merit Points had increased. If this continued, he had no idea when the drone could upgrade. Therefore, he wanted to gain some Merit Points from the South Korean warships.