Must have been less than 1200 when it started
Ratings

if you just start it is common to get huge gains in rating if you win your game because of the way this site calculates rating alternatively if you lose you suffer a huge loss in rating as well

I posted a thread like this a few days ago for a player who went 1498 - 1614 during a 1200-1500 comp. He had only played 7 games blitz, but had a standard rating about 1800. So he should have known he was playing against a weak field, and if he was me, wouldn't have wasted his time.
So check your "strong" player's profile and see if he wasn't actually better than he said
How is posibile to have rating about 1400 if you play in less then 1200 tornament?