Why does Zhuge Liang dislike Wei Yan?

Wei Yan, during the competitive period, because Wei Yan was a "free man" at that time, he took refuge in this today and that tomorrow, which gave a bad impression. But when Liu Bei knew that he was a generalist and wanted to take him in, Zhuge Liang advised Liu Bei not to take him in, saying, "This man will betray his master one day." Zhuge Liang's worries are based on other people's rumors, which is different from the current "seeking truth from facts". Wei Yan's temperament: leave immediately if you don't value your master. Wei Yan always wanted to take refuge in Cao Cao, but the opportunity did not appear. Seeing that the ministers who followed him left in succession, Wei could not take refuge in the chaos. After many twists and turns, he finally met Liu Bei. He wants to work hard for Liu Bei, because everyone says that Liu Bei is the kindest. Liu Bei really listens to Zhuge Liang, and it is Zhuge Liang who holds the military power. The use of beams did not give Wei Yan an important task, and the struggle between them had already begun since Wei Yangang came. In the campaign to pacify Meng Huo in the southwest, Wei Yan made several suggestions, but all of them were rejected by the conservative Zhuge Liang. Six out of Qishan, Shu basically has no generals, Wei Yan is the oldest in the army, but what he said has no power at all. Zhuge Liang took Jiang Wei as his confidant and continued to crowd out Wei Yan. Wei Yan's tricks are considered risky, irrational and inappropriate by him. It was precisely because Zhuge Liang was too "stable" and too conservative that he finally failed. After Zhuge Liang's death, Wei Yan's grievances broke out for many years, which led to the burning of the plank road. He wanted to be creative and conquer Wei. But Zhuge Liang, trapped by his men, killed him, and Ma Dai beheaded him. Wei Yan was accused of rebellion and became a sinner through the ages.