The results of British elections are seriously affected by outside influences like American-for-ownership-purposes Australian Rupert Murdoch, but we don’t talk about that because Murdoch supports the right - even the far-right - side.
The Murdoch (and French-for-tax-purposes) Rothermere Press has gone beyond mere partisanship to telling actual lies on the front pages, yet nothing happens. Double standards apply.
I still maintain that a democracy should be strong enough to withstand foreign pressure and non-military intervention. Where the US system failed was twofold; the media did a very poor job of fact checking on “news”, and so did the institutions of State like the FBI. The FBI and the CIA get paid to investigate stuff like this. They did a poor job.
The question of whether Trump was improperly funded or supported by Russia is a different matter. In the UK, Israel tried to intervene in the election, in support of the Right, via a diplomat - it was exposed and the diplomat was removed.
Again, did the agencies do their job?
Unless Russian hackers actually interfered with voting machines, the election itself was legitimate. The issue is why the State and the media were weak, and why the Democrats preferred a machine candidate.