In my limited opinion (9 years kick boxing, 3 years Ishin Ryu Ju Jitsu) I think Mariusz had a very good stance, good reactions and blocking skills and near perfect leg sweeps. I don't know where you saw the lunges?
If you have ever received a powerful sweep/ shin kick to the legs you would know that the pain is immense (not so bad for the kicker coincidentally). His opponent was shell shocked and that led to his downfall.
Considering it was his first MMA fight he fought very well.
Don't forget that he does come from a martial arts background. He is 4th Dan Kyokushin karate, this is a brutal no nonsense form of karate not to be confused with kata based forms such as shotokan. He hasen't walked straight from the bench press into the cage!!
To get an understanding: