The buyer's identity, and intention, remain a mystery. The move is likely a combined response to the turbulent political climate in the U.S., and to the ongoing Marvel Comics story Secret Empire, in which Captain America is transformed into an agent of Hydra, and becomes the fascist ruler of America.
The domain name was registered in 2014 through an anonymous domain registry. The redirect to whitehouse.gov was set up April 16. Prior to that, it redirected to 8Chan, an adult-oriented imageboard similar to 4Chan. Before that, it went to the official website of Senator Ted Cruz (R-Texas).
Newsarama reached out to the anonymous registrar of the domain, but has yet to receive a response.