A lot of confidence and a lot of stupidity too. Whatever the reasons behind deploying an S-400 battery so close to the front line, it is wrong.They where in clear view and not widely spaced.... maybe too much confidence. They where spotted with a UAV and didn't react to it, no system to hunt it or too small ??? If spotted, better to pack stuff and get away in multiple direction if you are not able to down it..
In my opinion, that would be exactly the reason. The Ukrainians want the Russians to escalate by responding to these attacks on the early warning system with tactical nuclear weapons, all of NATO's recent rhetoric of going to war if Russia attacks with nuclear weapons are not trivial, they are a message.Has Ukraine been in such desperation that they lure Russia into nuclear response and hope NATO direct intervention ?
See if the Russians will fall for it.