But there is plenty of oil in Russia! Why invade?
Stories, when well done, explore interesting concepts and can teach us about how some actions may turn out - yes a lot of writing is lazy and stupid these days, but it's hardly justified to write off all of fiction because of that.
This is backwards; if you want to see characters taking entirely unmotivated actions, Grimm's Fairy Tales is a great place to look. Modern writing is a lot more concerned with justifying what the characters do than traditional stories are.
That said...
> Stories [...] can teach us about how some actions may turn out
True stories can. Fiction feels exactly the same, but it doesn't tell you how the action turns out - it tells you how the narrator decided the action should turn out. This is often unrelated to what would happen in reality.
For the same reason the US occupied Afghanistan for two decades, destroyed Syria and toppled Libya. An attempt to strip Russia's influence out of the Middle East and wider region as a continuation of the eternal great powers conflict. The US has been conflicting with China across Asia, battling over influence, for decades in a similar way.
One of the highest ranking and most decorated generals in US history - four star general Wesley Clark - is on public record stating that this is the exact reason we did it, as told directly to him by his pals in the Pentagon as the plans were being put into action and before we wrecked Syria or Libya (both of which were on the list to come next).
Now the US is leaving Afghanistan and guess who is stepping into the regional great power void: Russia. And there's George W Bush now saying we shouldn't leave Afghanistan, he doesn't want the US to cede regional influence to Russia. Globalist warmongers are gonna be globalist warmongers.
Oil is a very distant consideration next to military dominion and regional influence/control. If the US wanted Iraqi oil, Saddam would have sold it to the US by the millions of barrels per day at any time the US wished it. Hell, Saddam would have sold it under the table at a steep discount. It was very obviously not about the oil. Oil is merely one of many strategic items on the board. Sometimes I think the warmongers in DC prefer the false "they did it for the oil" premise, it's preferable to the truth, that we smashed the US fiscally and got thousands of our soldiers killed, to spar with Russia over influence. But that's the same exact reason we invaded Vietnam, we weren't there for oil either, we were there for the influence/control over the region. We're also not all over Eastern Europe for the oil, either; again, it's the power conflict with Russia.
Don't we also have an obligation to support our allies? I don't think we should have become involved in Afghanistan in the first place, but after we've been there for nearly 20 years, encouraging the Afghans to fight against the Taliban, I'm not happy that we're leaving our allies to die. (Just as we did in Vietnam.)
Russia is a spent force. It's population and military are aging, its resources are stretched; it's more a nuisance than a menace. (This is fine. Britain was, too, after WWII.)
China is the real threat in the region, and it's likely moving into the vacuum. (For reasonable reasons. The Taliban can help secure their western border.)
> Russia is a spent force. It's population and military are aging
> China is the real threat in the region
> "Iraq's sector has remained state-owned and state-guided, and US companies have been forced to compete in open licensing rounds. Various efforts by US Administrations (including the current Trump Administration) to engineer bilateral negotiations and to promote US company interests have come to naught."
https://www.spglobal.com/platts/en/market-insights/latest-ne...