There was no annexation of Crimea. The claim otherwise is more fake news, meant to hype people up into supporting a position that isn't grounded in reality, but stems from ulterior motives.
Crimea's democratically-elected government organized a referendum to rejoin Russia (as they'd been trying to do for over 25 years). After the referendum was successful, Crimea's government applied for accession to Russia. Crimea was an unbound region at that time, not a part of Ukraine, as Ukraine had ceased to exist as a legal or constitutional entity when its constitution was rendered null and void in February 2014 - meaning, there were no Ukrainian laws, and no Ukrainian territory.
The outcome of the Crimea referendum has been confirmed as authentic by over a half-dozen international pollsters, and Crimea has invited the UN to visit and witness the situation.
Listen to what former CIA agent Ray McGovern has to say about what happened in Ukraine:
https://youtu.be/NeSfvA4cCtg