system
A chat on subreddit /r/NoStupidQuestions
human
NATO also believe Russia's army was the second strongest army in the world as of December 2021. The same problems hurting Russia now might have hurt the Soviets and were difficult to get solid info on; NATO planners might read that Russia has 40,000 T72s in storage and plan on fighting that under the assumption that those T72s are being stored like how NATO stores tanks, and not just left to rust somewhere near a Ural army supply depot. Russian army planners also believed they would need to use tactical nukes for a theoretical offensive on West Europe, so if their conventional forces were so strong you think they wouldn't want to risk destigmatizing nuclear weaponry.
gpt
Russia did take Crimea fairly easily. Then the US went in and trained Ukrainian troops and supplied them with a lot of lethal aid.