This is insane ... How can people be cadets, and then fired for no reason?
It - the "no reason" - was called September 11th. Within days of that event Aer Lingus took the view that the aviation industry was going to change radically and permanently. The then Chief Executive of Aer Lingus (and current C.E.O. of British Airways) believed that Aer Lingus would not survive without severe retrenchment. He took kind of decisive action that most carriers chose not to take at the time. This included cancelling all cadet classes before the pilots concerned formally entered Aer Lingus, redundancy, etc. There was one year of losses and Aer Lingus has been profitable since that time.
It is understandable that the decisions made at that time had very unpleasant consequences for the cadets involved (though nobody ever mentions that there would have been no work for them if they had become full time employees). However, by all accounts their interests have been carefully looked after by IALPA in the interim.
Mr Chris I note you are from the U.S. where pilots are furloughed all the time. You may not be aware that such a facility is not available to most carriers outside of the U.S.