Russia "annexed Crimea" giving them some of those goals but they have only one way to reach it by land via a bridge and a long detour. Extending the "annexation" to the whole of south east Ukraine gives Russia two alternate land routes into Crimea and complete control over the Sea of Azov.
In my personal opinion, the invasion/annexation/war was always about Mariupol and a unbroken land corridor across the northern coast of the Sea of Azov. Everything else is a smoke screen/distraction/false pretext.
Material factors:
- Gas in Ukraine. Not only pipelines, but apparently there's plenty of reservoirs.
- Apparently there's also a pressing issue with water in Crimea.
- Industry. Ukraine retains a lot of industry and expertise from USSR, including expertise about how to build and maintain some of their nukes. Many advanced stuff was designed in Ukraine too.
- The buffer doctrine. Just put as much land between you and your potential enemies, as europe is pretty much a cone plain from Berlin to Moscow. Russia is pretty much indefensible on that regard as there are no natural accidents to help stopping enemies.
Inmaterial:
- Some shared views by the russian intelligentsia close to Putin and Putin himself, about some ehtno historical views about Russia, the Russians etc. Not clear how much this plays a role, and it's not yet clear to me what is it about, but they say it's there.
- Too many yes men around Putin. Aparently FSB and other agencies told this people what they wanted to hear. It's not clear to what extent this is common, but apparently they all believe this has a high probability of being true for at least this very issue.
Probably some other stuff I forget. They have been focusing on trying to get some sanity on TV, but without much success.
This scene in Spain is interesting as there's a retired General (Pedro Baños) who has been very hostile with this people. Before the invasion he mocked them as being NATO mouthpieces. He has a large following in Spain, so despite they try to ignore him, they get a lot of heat for it.
Long explanation: https://acoup.blog/2022/02/25/miscellanea-understanding-the-...