They didn't have 200k troops and tons of military gear amassed around their borders for 8 years. It's hard to believe anyone who's been paying attention to the buildup would've thought they're there just to chill out.

It's true, but I tend to think humans are pretty bad at threat evaluation if the threat lasts for years and years.

Kind of like the IT admin that doesn't check backup integrity often enough because there's never been a data loss issue in years.

Or conversely, when you have a flappy monitoring system that constantly complains about non-problems and half-problems, it gets very hard to notice when an actually serious alert is firing.

It's not entirely true. Someone who lives in Eastern Europe these border drills and threats are normal and go back to 10 years and more. Obviously this time they were better equipped infrastructure wise that the western agencies clearly said they were but for an average citizen it was "the same as usual".

Isn't this partially why armies are routinely sent out on "war games" or "joint manoeuvers?

You're never sure whether the Chinese submarine is "exercising its rights to international waters" or is preparing for a strike; or the US-Swedish troops are just making friends with each other or getting ready to invade.

That's totally apart from the obvious "sabre rattling" bit.

Even if that’s true, Putin straight up announced he’d be sending troops into the two rebel controlled regions a few days ago. That’s a pretty obvious sign that this time was different.

Like, I get that the previous buildups could be dismissed as saber rattling and training exercises, but Putin literally announcing, "HEY I'M COMING IN, I'M SENDING IN TROOPS TO UKRAINE NOW", how do you dismiss that?

You mean for Russians in Donbass region, right? There were 13 thousands civilians killed there over 8 years.