Have I got this right? You phoned the owner of the house next door but one, with your concerns about their tenants, after your next-door neighbour asked you to support them in THEIR complaints. Then next door told them next but one that YOU were the ones who were complaining.
And you are now annoyed at next door for putting you on the spot. You helped them, and they put the blame on you, so you are getting the flak from the ones who are having to move?
They weren't very grateful, were they? Perhaps the others were too intimidating, and they chickened out of admitting it was them. But you do have to live next door to them, so it would be a mistake to fall out with them. After the others have moved on, say to next door how glad you are that they are gone, but you do wish your life hadn't been made worse by being identified as the one who stuck your neck out - on their behalf. Don't say it as a complaint, just as a comment in passing, and then get on with staying friendly with them.
I do hope you don't get anyone even worse in the house next but one!