It is almost certain that this was done with the active agreement of elements within the Reagan administration, and the passive acquiescence of the Holy See in Rome.
John Paul II was determined to extirpate what saw as left wing elements in the Church, and making noise about Romero's murder was inconvenient when viewed through the lens of this agenda, (on edit) and so the silence on the assassination.
Well, Pope Francis just Beatified Archbishop Romero:
The Salvadorean archbishop Óscar Romero was beatified on Saturday, the final step before sainthood, 35 years after he was shot dead at the altar by a rightwing death squad for denouncing the oppression of the poor by the military dictatorship.This, along with the sainthood for John XXIII, show a clean break for this Pontiff with his reactionary predecessors, though his longest term impact might be on cleaning up more mundane corruption in the finances of the Papal bureaucracy and the Vatican bank.
Roman Catholics from around the world mixed with former Marxist rebels from El Salvador’s brutal civil war as more than 250,000 people gathered in the capital to celebrate the country priest who confronted a US-backed government.
Cardinal Angelo Amato, sent by Pope Francis, officiated the ceremony that followed decades of debate over whether Romero had rejected Church doctrine by embracing radical, leftwing rebels. [Actually the record shows that he was no fan of the rebels either, he opposed violence on both sides]
Born in 1917 in a mountain town near Honduras, Romero apprenticed as a carpenter as a boy before entering the church, where he rose through the ranks, appearing to be a quiet conservative.
But soon after being appointed archbishop in 1977, he became a staunch critic of the military government after it began killing, kidnapping and arresting priests who had been organising peasants and supporting workers’ rights.
His sermons, often broadcast on radio, riled rightwing extremists. But he ignored multiple death threats, remaining defiant up to his murder while giving mass in the chapel of a San Salvador hospital.
“In the name of this suffering people, whose cries to heaven become more deafening each day, I beg you, I beseech you, I order you in the name of God: stop the repression,” he said in a speech to government soldiers the day before his death.
Time will tell.