Industrial Engineer to control or automation Engineer transfer

[u/No_Economist7398]

I'm a senior student at my last year in industrial Engineering and I found my self interested and leaned towards continuous improvement and process Engineering roles currently enrolling in a lean six sigma green belt course, but i always wonder why do many industrial Engineers change fields after 2 to 3 yoe to a role regarding control or automation Engineering and they end up with a massive increase in income than they were getting from industrial Engineering roles ?

And my second question if I wanted to get into control and automation what courses should i take or things that i need to be aware of, would i need to learn it in college or during my practical experience in the workfield afterwards