Of course its not down to 1 man. That would make football management too easy and any tom,dick and harry could do it then.
Alonso, in his last season, was monumental and his passing sorely missed. However, how many remember his passing and losing the ball before 'that' season? Was pretty much the same as Lucas now - if not worse.
Also, tell me why Alonso and Arbeloa would still be here today even without the falling outs and club instability. I am pretty sure that these players would not resist a call to R.Madrid, unless they were playing crap.
So IMO, Alonso & Arbeloa would not be here today regardless.
And the reason why it all went wrong is a combination of many factors:
1) Big reliable players left/sold
2) Could not get equivalent replacements to join us
3) G&H did not have a healthy relationship with any of the management and directors, and mainly Rafa who was probably the only one fighting for the football aspects of the club.
4) Club put up for sale - major loss of morale to all employees
5) The Club has still not fully stabilised and needs a bit more time before everything is set in place and therefore can provide security to the staff.
We have to imagine if we were working at a job and the Owners were jerks, the management did not get on with them, the constant 'washing of dirty linen' , and you know this company is looking for new owners. How would we react?