In choosing Anthony Scaramucci as White House communications director, President Trump has appointed a financial showman who rivals Mr. Trump’s own outsize knack for self-promotion.

Mr. Scaramucci made a fortune on Wall Street, but he gained fame on CNBC and in Las Vegas by defending the financial industry at a time when it had few public supporters.

After the financial crisis, President Barack Obama criticized Wall Street’s big bonuses, and several banks canceled their opulent annual conferences amid public anger over the federal government’s bailouts of financial firms. Mr. Scaramucci filled the void, holding his first hedge fund conference in 2009 at the Wynn Las Vegas hotel.

The next year, Mr. Obama answered questions at a town hall-style chat broadcast by CNBC. Mr. Scaramucci, a former Harvard Law School classmate of Mr. Obama’s, voiced the complaints of some people on Wall Street who said the president was treating them like a piñata, “whacking us with a stick.” He followed that by appearing in Oliver Stone’s sequel to the movie “Wall Street.”