In my opinion, this can explain that strong teams included in low quality league, but cannot explain weak teams included in high quality league. In my experience, most of these abnormal teams do not change significantly after league drawings. The strong team may release or sold their weak unsigned players and so its active players have no big change. However, it is quite weird that those weak teams do not sign those high quality players to replace current players.
It is quite difficult to investigate ourselves. Some information required should be obtained from our own teams or our friends' teams. I have already given to study the method of drawing. Personally I prefer pure random drawings for all competitions.