Yes, it will be interesting to find out why Poles behave strangely when they are on the plane.
They never used to until cheap airlines made air travel accessible to "a different class of person". ;) Most of the scumbags used to take the bus, but now it's cheap to fly.
I've never seen a Pole misbehave on BA, LOT or Sabena. The pushing and shoving comes from no allocated seating. If you have a seat number, there's no hurry is there?
I'm not a snob though. I like cheaper tickets too, so I fly budget airlines, but think of it more as a fast bus, than the "luxury travel" flying used to be.
So to answer the question, it's because they have not been trained in the proper procedures. Ryanair always has their announcements in English first and often no Polish speaking flight attendants.