Washington is chock-full of foreign influencers.
I’m not sure I’d characterize the investigation as “failed,” though. It has (so far) accomplished what it was supposed to: Cover up the wrongdoing of 2016 (and before) and cripple the Trump presidency. Though the former is starting to unravel, I hope.
Why do you call the Mueller investigation failed?
It succeeded — at finding the truth.
It failed because Trump didn’t get goaded into a process crime that would allow the DOJ to remove him from office.
The DOJ has no power to remove a president from office, or even indict him for any crime whatsoever. Only Congress can remove him from office, and only then can he be indicted.