Trouble is, the scamsters can get such a hold over people, and unless the person has been shown to lack capacity, there's really nothing you can do, since the law takes the view that people are free to throw their money away if they wish.
I found out a while ago that an elderly neighbour had fallen for a so called 'lottery' scam, I.e. someone phoned her (pretending to be from NatWest as I later found out) and told her she'd won a million pounds (on a lottery she had never entered for) only of course she had to make a payment for 'tax' first..
By the time I found out, she had made umpteen of these payments, at least £4K a time, to people abroad.
Dh and I told her very bluntly that it was a scam, they were just criminals, but she wouldn't have it, she believed them utterly. They tell their victims not to tell friends or relatives, since 'they'll just be jealous and try to prevent you from getting your prize.' She would not go to the police, or let us do so, and if she wouldn't even talk to them, let alone make a complaint, there was no point in us contacting them.
In the end her children put a block on her phone and had her mail redirected. By then her dd told me she thought about £100k had gone down the drain.
Previously I knew she had been addicted to those Wordsearch 'competitions', where you very conveniently phone in all your details at God knows how much per minute. Lists of likely victims who do this sort of competition are sold on in 'suckers' lists' - they do actually call them that.
There is a website called Think Jessica, all about various scams largely targeted specifically at the vulnerable/naive elderly, It makes very scary reading, but anyone with such potentially at-risk relatives should read it.