Leading up to? Cherry picking a small time period is not a good look. Decades of Russification and displacing Crimean Tatars (and straight up starving them) damn near eliminated them from the peninsula for years. In 1989 Crimean Tatars made up 1.6% of the population compared with a third 50 years prior. After a couple decades with Ukraine, about 11% of the peninsula are Tatars now.