The context of this story is even sadder than the headline suggests. The 50,000 incarcerated people who were given suffrage are actually those who have been in prison without actually having received their sentence yet. The total prisoner population in Mexico is over 232,000.
This came about only after two indigenous people were arrested and held in prison since 2002 while they were never told what they were arrested for in their native language (they didn’t speak Spanish). Apparently they were tortured too. All the time they never received sentencing so they were still technically innocent and were granted the right to vote in 2018.