The only possible reason I could find was that Mr Mawbey was refusing to pay Jimmy and his workers any more money until the job was completed, to his satisfaction.
Until Mr Mawbey, who gave Governor the contract for a fencing job, discovered that the job was not being done properly, he appears to have been paying Jimmy a regular salary.
He claimed in court that Jimmy had been earning around 6/- a day.
This appears to have been a more than fair amount.
A recent Who Do You Think You Are program about Australian Aboriginal Olympic gold medallist, Cathy Freeman, revealed that her grandfather was paid the same amount when he was a soldier in the army during World War I, some 15 years later.
And a former nurse recently told me that she was paid 15/- a fortnight in the 1930s (on top of accommodation and food), as was an apprentice milliner.
When Mr Mawbey and discovered that the fencing job was not being done properly, he could have sacked Jimmy Governor for failing to uphold his contract.
But it was very hard to get farm workers in those days.
The job seems to have carried a stigma because the first farm workers had been convicts, and a form of cheap labour.
So in order to attract and keep them, the employer would have had to have been prepared to pay good money.
Mr Mawbey may also have had a time limit imposed on him to have the fencing job done.
One of the conditions imposed on selectors by the government was that they had to improve the land they were leasing.
Banks may have imposed a similar condition on farming loans.
A good fence was an asset that improved the property; a poorly constructed one brought its value down.
Mr Mawbey has been criticised for taking the faulty fence posts away and giving Jimmy a crown for them.
But all they were good for was firewood.
They would not have been used for fencing anywhere else on the property.
Governor's friend, Jacky Underwood, said during his court hearing that the cessation of a regular salary as the reason why Jimmy had a grudge against Mr Mawbey.
A travelling hawker, Sam Ellis, claimed to have seen the Aboriginal men making traditional wooden clubs, weapons, at their camp after their fencing work had been rejected.
I think the truth of the matter is that they planned to murder all the Mawbey family and then take whatever money in the house that they believed was rightfully theirs.
I believe the allegations of discrimination against his wife and himself were all manufactured to create a smokescreen around the true, and much simpler, cause of the murders.
Jimmy appears to have been paying Jacky Underwood and the three other males to assist him with the fencing job.
Whether he had let Mr Mawbey know he was going to sub-contract part of the work when he was awarded the contract is not known.
However, Jimmy later made out that the others just 'turned up', out of the blue, when in fact it appears to me to have been pre-arranged.
This suggests he had not been 'up front' with his employer in the beginning.
Of the four men, only one, his younger brother, Joe Governor, could be described as 'able bodied'.
Jacky Underwood was blind in one eye and had an injured foot that caused him to limp.
Jacky Porter, was an old man, although judging by a subsequent report, fit and active.
And the 'boy', Peter Porter (aka Governor), was deformed.
It is not known if Mr Mawbey knew about or understood the kinship obligation Jimmy appears to have had to support the three men, even though they were apparently incapable of doing the job properly.