because I would have thought they'd have owned Ukraine within the first two days of an invasion. These days I'm never quite sure what to believe when I see it on the news.
War is not a computer game to have an easy outcome.
US invaded Afghanistan more than 20 years ago and spent $7 trillion and couldn't achieve anything at all there. They were fighting cavemen (literally) who had no airforce, no radar, no missiles, no tanks, so support from any other country, not even half decent weapons.
In comparison Ukraine has a military, has airforce, radars, tanks, missiles, and receives billions of dollars of support.
The goal was never to occupy entire Ukraine. The goal was to annex east and south of Ukraine that are strategically important to Russia and leave the rest. Half of Ukraine doesn't want Russia while the other half does. They can never rule over that first half, so they would remove Zelensky with someone who that other half can accept but is at the very least anti-NATO if not pro-Russia. The first part of the plan is already over.
Funny enough, this is similar to what US tried to do in Afghanistan and failed because unlike Ukraine, nobody wanted US in Afghanistan so they were kicked out in defeat.
Question from a citizen of Ukraine, who has worked in the eastern regions for almost 10 years.
Well, for starters, let's discard the forcibly implanted narrative that in the east they don't want to be part of Ukraine, but they want to be in Russia, or against the Ukrainian language, or someone banned the Russian language. It's all 100% false! If you want, I'll tell you separately what reality looks like on these issues.
So. the eastern and southern regions do not want to go to Russia. They want to live peacefully and develop in Ukraine. And in order for you to understand the real situation, you need to remember one historical fact! From the 30s to the 70s of the last century, the eastern and southern regions of Ukraine were essentially subjected to genocide, and a significant part of the Ukrainian population was either destroyed or evicted to the far east of the Republic of the RSFSR (now it is Russia), and they were settled in their place ... Guess who? That's right - immigrants from the territory of Russia! That is why there are a noticeable number of pro-Russian (specifically pro-Russian) separatists in these areas. But they are by no means the majority! It was a small digression into history.
Regarding NATO - I will say this, NATO, as an international organization, showed itself in a critical situation ... NO WAY! More precisely, not at all as a defense alliance, against any aggressor or global terrorist! And I'm not sure that now Ukraine will strive to join this union, because. NATO, with its formality, will tie us hand and foot, and we will not be able, in the future, to immediately respond to risks from Russia (if it remains after losing the war to Ukraine). And this means that the factor dividing Ukrainians, in your opinion, is likely to disappear. Also, after the victory over the Russian terrorists, most of the separatists will disappear from the territory of Ukraine. This means that there will be no separating factors in Ukraine, or their influence will be minimal.
Well, about the goals of Russia. Well, let's assume you're right. They need the eastern and southern regions. The question is - why are they now just totally destroying EVERYTHING? If they needed industrial infrastructure, Russian terrorists destroyed it themselves. If they needed a loyal population, they destroyed it, and crippled the lives of those who remained alive. It turns out they need bare land with ruins and mass graves? Well, it's stupid really. And I'll tell you, the answer to the question of what Russia needs, in Putin's feverish delirium, is his "my path", which he recently announced - the restoration of the USSR-2, the restoration of "greatness", right up to the borders of the Warsaw Pact. The Warsaw Pact is an adversary of NATO, the majority of whose participants are now praying that only the "Russian world" will not return to them. It included the USSR, Poland, Bulgaria, Romania, Hungary, East Germany, Czechoslovakia, Albania (I don't seem to have forgotten anyone). This nonsense of Putin is their goal! More precisely, Putin! And he realizes all this with the lives of Russians worthless for him. And any totalitarian-terrorist-kleptomaniac regime always "devours itself".