Financial Sector Growth

Brad DeLong: America’s Financial Leviathan: Project Syndicate discusses ways the financial sector can help the economy, and mentions the sector’s justification for its growth:
“not, by and large, been a bad thing….Deploying capital to the places where it can be best used helps the economy grow…”
But if the financial sector was helping the economy grow, then the sector’s share of the economy would not be increasing so much, because the economy would be increasing.