The video above shows you How To Make Crash Videos In BeamNG.
With the latest BeamNG update there is two methods to creating crash video.
Method 1 (Old) - Is using the Replay UI app to record a replay and then going back and free caming the camera to get the best camera angles of the crash
Method 2 - Cinematic Camera mode camera automatically puts the camera in a cinematic position before a crash happens. This makes it easier to make crash videos however it's less reliable and you can't go back and re-cam the crash.
Please note that you will need a recording software such as OBS to record the video clips.
This video is just to show you how to cam the crashes in game.