What is Zhuge Liang posting gossip for?

It is said that Wu and Shu are at war. Mr. Zhuge didn't want to fight with Wu Da and cause unnecessary losses. At this time, his enemy was Wei. Once attacked on both sides, it will be very passive and beneficial to Wei. So he set up "Jiugong Bagua Array" (full name) to trap Xun. Finally Mr Zhuge's father-in-law took him out. Lu Xun felt that he was no match and quit.