RIYADH, Saudi Arabia — One day in November 2015, Saad Almadi typed out a 14-word post on Twitter about Saudi Arabia’s deputy crown prince.
“Mohammed bin Salman has taken over the economy, defense and everything under the king,” he wrote, replying to a professor who is a fierce critic of the kingdom’s monarchy.
A Saudi-American dual citizen living in Florida, Mr. Almadi had little reason to believe his post would attract attention. He was a retired project manager, not an activist, and his words were largely factual — Prince Mohammed had taken control of many of the levers of power since his father became king that year. By 2017, he would push aside a cousin to become heir to the throne.