So, Cassiopeia was too big of a lane bully and had to be reworked
Taken from patch notes:
"As a lane bully, one wrong move against Cassiopeia can lose you a ton of HP and send you ducking for cover beneath your tower (or just packing your bags and going home)."
"As a lane bully"
"A lane bully"
So, they basically admitted the rework was a failure since it didn't even accomplish what it should.