DUBAI, United Arab Emirates—Saudi Arabia on Saturday executed 81 people convicted of crimes ranging from killings to belonging to militant groups, the largest known mass execution carried out in the kingdom in its modern history. The number of executed surpassed even the toll of a January 1980 mass execution for the 63 militants convicted of seizing the Grand Mosque in Mecca in 1979, the worst-ever militant attack to target the kingdom and Islam’s holiest site. It wasn’t clear why the kingdom choose Saturday for the executions, though they came as much of the world’s attention remained focused on Russia’s war on Ukraine—and as the U.S. hopes to lower record-high gasoline prices as energy prices spike worldwide. British Prime Minister Boris Johnson reportedly plans a trip to Saudi Arabia next week over oil prices as well. The number of death penalty cases being carried out in Saudi Arabia had dropped during …