DL 262, JFK-CDG, has been delayed half an hour to one hour the past six days https://www.flightaware.com/live/flight/DAL262 and is estimated to be delayed again today (DL app).

Is there a reason for this or is it just a series of random events?

Is immigration/passport control likely to be any better (or worse) for a 9:30 to 10:00 arrival rather than the scheduled 9:00?