I recently watched a YouTube video titled "Dangerous Crosswind Landings during a Storm at Düsseldorftitled" and witnessed at the 2:06 mark, a twin engine commercial jet aircraft landing and noticed only one thrust reverser was deployed.
I am looking for a knowledgeable answer, asking if this was a malfunction.
It is impossible to tell from the video what the reason or cause was, this is all speculation.
Most likely it was a malfunction of the thrust reverser. There is a good change that the crew was aware of the problem before take-off; the Airbus A330 may be dispatched with one or even both thrust reversers unserviceable according to the minimum equipment list (MEL)
Another possibility is that the crew accidentally only activated one thrust reverser. Given the firm landing (as it should be given the strong crosswind) they might have erred in the heat of the moment.
It is unlikely that the decision to use only one reverser was on purpose if two reverser were serviceable. On the ground the aircraft has a tendency to weathercock into the wind because of the vertical tail. Selecting only the windward thrust reverser aggravates that tendency.
