On a site like this, that crane is used mostly for area wide lifts of mostly light weight items like a pipe or beam in the lay down area that is shown. That is also not a giant crane. Definitely operator error, he should know his boom length, lift weight and use corresponding charts inside of cab showing maximum boom angle.
Or the load was over 1000#
After watching the video several times, I noticed the crane didn’t tip over directly over the front but went down off to the right. It does not appear to be a crawler crane but rather a wheel crane and if so I wonder if the out rigger cylinder failed during the lift. Blowing a seal could have definitively caused that incident.