Well, we have to remember that we're dealing with the State. By which I mean, State-affiliated institutions. Therefore, cover-up will be innate. It's just the way they do things. 'The State' has a particular character, it is basically like a rotten firm or office, only every avenue you seek will be rigged, be it the local NHS CCG, the local Council, the NHS primary care trust, the police (sister organisation to the Council) and right up to the GMC (in this case) and also the NMC is manifestly corrupt.
These State-affiliated bodies can use the State machinery to orchestrate any cover-up of any wrongdoing. I should point out that they don't quite see it as 'corrupt' - rather it's ensuring the system works really well and is watertight. You make a complaint, it goes nowhere, it is not upheld - therefore nothing to see here! Anyone decent who raises concerns gets smeared and shafted.
As for why, well, it's simples. Dead bodies save the State a fortune. Save the local NHS CCG a fortune in medication, the Council a fortune in adult social care, you are working through a backlog.
Some day someone will look at the low hydration levels in Surrey care homes and figure out what is going on. Is it, say, a policy? In the meantime, it will take 30 years for the truth about this to emerge, but I'll point out that corporate murder via dehydration is a lot safer for a local authority/NHS CCG than using opiates, which of course leaves traces.