"Russia is behind the problems in our country" is the Liberal's version of the Far-Right's "Immigrants are behind the problems in our country" - blame the foreigners rather than the extremely wealthy people who own the news media that relentlessly pushes this shit and subsidize far-right politicians and lobbyist offices and hard-neoliberal "Think Tanks" pushing for laws that help their economic interest whilst making life worse for everybody else.
Specifically for Britain and Brexit, it takes some seriously selective memory to "forget" how the Newspapers owner by Murdoch and the Rothermere family were pushing extra hard nationalism and anti-immigration for decades in the run-up to Brexit, very openly for people voting Leave during the Referendum and some seriously unhinged takes on how Britain should negotiate the Exit Treaty with the EU.
Also, don't get me started on how the choices made by both New Labour and Tories in the aftermath of the 2008 Crash, both the unconditional saving of the wealth of the Asset owners (both the way banks were saved and the choices of the BOE which went way beyond just setting interest rates and even included buying corporate bonds from selected companies) and making most of the population pay for it with crushing Austerity. very much plowed, fertilized and seeds the field upon which Brexit was born.
Next to what was done by 100% local billionaires and their politician minions, foreign interference was minuscule.