Earnings from the nation’s three biggest banks backed investor hopes that a Trump presidency would bring less regulation and stronger economic growth that reinvigorates the financial sector.

The fourth-quarter performance of J.P. Morgan Chase & Co., Bank of America Corp. and Wells Fargo & Co. was largely in line with what Wall Street had expected: Trading revenue was upbeat thanks to increased market activity and volatility following the election; expenses remain in intense focus; credit quality continues to improve;...