Let's look at the video. Right hand spiral descent at very low speed is symptomatic of a low Nr condition with low tail rotor effectiveness and a relatively high collective position. The reasons for the potential low Nr condition are unknown but the low nose attitude is indicative of an attempt to regain airspeed while disk authority is borderline effective. The successful arrest of the RoD to survivability may have been based on flare increasing Nr, hence tail rotor thrust and overall reduction in descent.