One of the reasons is Ukraine is having to move these vehicles through their own minefields. The dirt track there driving through was cleared of mines ahead of time but even to Russian drone observers it's obvious what that track is going to be used for so drones just loiter until the convoy arrives at which point artillery is called in. I was saying yesterday they should have a team scouting ahead of the convoy making sure there are no drones in the area.
Better yet if Biden hadn't dragged his heals on providing F-16's for the last year this likely wouldn't have happened.
The collective west has dragged its feet in arming Ukraine in what it needs to achieve victory and still does.
All plays into Russian hands, they are happy to soak up losses forever.