It does seem astounding, but I guess some of these guys are very good.
I'll admit, for a laugh I accepted the FB friend request of an 'American doctor stationed in Afghanistan', to see how long it would be before her desperately needed 10,000 quid.
He was not very good.
He couldn't speak good English, he did actually voice call me, making it even more obvious he was not American.
Sadly, also quite boring in that all he could do was repeat stuff about 'I love you' 'I miss you' 'I can't stop thinking about you'. Although it was quite funny when he tried to talk sexy. 
I gave up after a few days as it got pretty dull.
I don't know if he was delusional of if he'd had some success - I can only imagine someone like that getting somewhere with someone desperately lonely who also doesn't speak much English. But then if her English was so bad she couldn't see through this guy, I doubt she'd understand requests for money.
But I know there are much more sophisticated scammers out there. I read an account once by a woman who was obviously not dumb, but this guy drew her in in such as way that alarm bells didn't ring when he every meeting was cancelled due to escalating (and expensive) family emergencies. Reading about it, it seemed obviously, but evidently not when you're the target.