Polarisation of wealth

It has been reported that the wealthiest 5 families in the UK are worth more than the bottom 12.6 million. I imagine that each year the disparity in incomes becomes wider.
The question is this: what do these top families do to earn this wealth? Do they make things or harness the worlds natural resources to energise the country? Do they grow things or otherwise exploit the riches of the earth, perhaps getting their hands dirty? In other words do they make their money by honest toil or are they non retail bankers and other parasites in the financial industry who prey on the hard working others?
What is the motive for this accumulation of money? Is it greed or a lust for power? Can it be that once on the conveyer belt of wealth accumulation it is impossible to get off in some sort of self-perpetuating system like the growth of bacteria in a petri dish. I don't know. What I feel is that enterprise and hard work in the fields described above should be rewarded but if the capitalist system continues to polarise wealth through financial exploitation, then surely it is non sustainable. As the song predicted...there'll be trouble ahead.