Why did Mukul Roy return to Mamata Banerjee after 4 years?

There has been a big political change in West Bengal. In 2017, Mukul Roy left Trinamool Congress and joined the BJP. Mukul Rai created a favorable atmosphere for BJP in Bengal for 3 years, increased BJP's strength. But now Mukul Rai has returned home. But why did Mukul left BJP and returned to Didi? Watch this report.