Russian Army Losses in Ukraine

Pretty easy to answer, cameras are cheap and everywhere including the invasion.

All drones are flown with cameras for the pilot so its not difficult to also capture the film and share each strike. Magyar for example has as YT channel and you can see all the strikes his group make on the Russian fleets in the Black Sea.

If anything the numbers counted by Ukraine are very conservative, because they only count confirmed kills. If you blow up a van, its not exactly possible to count the dead inside.

The real crazy thing about this is how Russia continues to get tens of thousands of volunteers, each and every month.