The Monarch owners, quite simply, didn't wish to meet their obligations to the Monarch Final Salary scheme.
The UK government, and the PPF, were next to useless under pressure (and threats of closing the company) from the Monarch owners.
BA/IAG may be profitable but if they have no desire to meet their obligations (and the deficits) in the various DB pension schemes that their employees are part of - they won't meet those obligations.
BA/IAG will have watched, and gained confidence, from the employer handling of the Monarch and British Midland FS pension schemes.
The more aware employees of BA would have watched what was happening at MON and BMA and would have , quite correctly, been worried.
What happened at Monarch and British Midland, in respect of pensions, was criminal.