line (one's) (own) pocket(s)
To make a large amount of money for oneself in a way that is considered greedy or dishonest. The phrase typically implies that one is prioritizing making money above some other, more admirable goal. He doesn't care about creating some digital utopia—he's just trying to line his own pockets. This new contract is going to line our pockets for years.
See also: line
line (one's) pockets
To make a profit, especially by illegitimate means.