So since we are talking about what Putin said, here are the two most relevant speeches he gave on the telly:
2022 February 21:
-redacted-
2022 February 24:
-redacted-
The two together is about one and a half hours... I suffered through them. And made notes too. The videos are "hand translated" by an American prof (Phd in international relations) who knows Russian, so it's not ML crap.
Yes, in both videos says the territories were part of Russia historically, but the reason to launch the "defense" (as he called it) is different.
tl;dr
1. NATO expansion (security reason #1)
2. prevention of an attack against Russia itself (security reason #2)
3. genocide of the Russian minority in the Donbass
Long version:
He spends a long time to describe how relations deteriorated between Ukraine and Russia. He points at US foreign policy as the main reason. He talks about NATO expansion towards east and the creation of NATO military infrastructure in Ukraine, about the frequent exercises there, the various US basings (air and naval), etc.
He points out their disregard of their own promises that NATO won't expand, the rejections of Russia's propositions.
He notes the possible speed of attacks by various missile systems from Ukraine, and the possible reach of them.
He talks about the radicalization of Ukraine, the growing influence of militant nationalists who he frequently refers to as neo-Nazis. How the West helped to nurture anti-Russian sentiments, and how the prosecution of the Russian ethnics begin and intensified. He says radicals kept the Donbass under siege, they planned to bring the war to Crimea, and they declared claims on other Russian territories.
He says Kiev had/have plans of acquiring nuclear weapons as well.
Furthermore he lists the various agreements and treaties NATO violated, and the unwillingness of Kiev to implement the Minks Agreement which could have solved the issue in the Donbass and preserved Ukraine's territorial unity.
He talks a lot more about various stuff, like the support of terrorist organizations and attacks against the citizens of the Russian Federation and stuff.
In the first video he declares of the recognition of the independent people's republics in the Donbass, in the second he announces the launch of the SMO, citing the collective defense of Article 51 of UN Charter.