It is currently impossible to demilitarize the occupied Crimea as Russia has deliberately turned it into a military base from which it is trying to scare everyone away.
Russia's War Against Ukraine
UkrInform: Kuleba says Russia deliberately turns Crimea into military base
Russian President Vladimir Putin (L) watches the joint drills by the Northern and Black Sea Fleets from onboard the cruiser Marshal Ustinov in the Black Sea off the coast of Crimea on Jan. 9, 2020.