Crimea was generously "given" to the Ukrainian SSR by Khrushchev - who, oddly enough, was himself from Ukraine - in an impulsive act which was probably illegal under Soviet law.
Lots of things were probably illegal under Soviet law, like forced mass starvation and mass deportations of Tartars from Crimea.
Ukraine proclaimed itself an independent nation in 1991.
And Crimea promptly decided they wanted to be Ukrainian.
Please understand clearly that this was the very first time in the whole of history that a Ukrainian nation had existed. The name "Ukraine", itself, means "borderland" - that is, the borderland of Russia. For many centuries, long before the USA existed, Russians spoke about "Great Russia" (which became modern Russia, based on Moscow), "White Russia" (which is still known as Belarus today), and "Little Russia" (the Eastern part of Ukraine).
I wonder how my ancestors emigrated Ukraine ~120 years ago? Were they time travellers or does the question of what an independent nation is get very confusing once you start going back through history?
After the violent, illegal coup d'etat which overthrew the legally elected Ukrainian government in 2014
If you don't want a forced resignation don't open fire on protesters.
- of which George Friedman, founder and CEO of Stratfor (https://www.stratfor.com/), said: “It really was the most blatant coup in history"
A coup followed by an open election which the coup leaders lost.
the Kiev regime instigated extreme violence against Russian-speaking Ukrainians.
As exclusively shown on Russia Today (and I mean exclusively).
The population of Crimea voted overwhelmingly to become part of Russia again
"Do you want to join Russia?
a) Yes I want to join Russia.
b) No, I understand you're not really asking.
c) Are you even going to bother counting this or do you already have the results typed up?"
and the Russian government agreed.
How generous of them.
Putin did NOT "annexe" Crimea. He allowed the people of Crimea to become part of Russia again, after a relatively brief period in which they were subjected to a freshly-created foreign power by a series of administrative freak events.
Like Putin sending in Russian troops to take over Crimea, installing a former mobster from a fringe party as a puppet Prime Minister, and then holding a fake vote vote to join Russia.