As others have pointed out, there's lingering resentment from the cold war, general Russophobia, and the villification of any nation that doesn't allow itself to be entirely subsumed by western (American) capital and military hegemony.

It was also supercharged after 2016, when liberals with needed a non-material reason to explain how the US elected Trump and the UK voted for Brexit, that didn't either A) blame liberal 'centrism's total failure to improve or even maintain people's material conditions or B) reveal uncomfortable truths about the power structure and institutions of so called 'western liberal democracies'.

But even before those seismic shocks to the liberal worldview, primarily British & American intelligence services had begun spinning up a broad network of new cutouts and propaganda arms focused on reviving Russia as a threat to discredit potential left political resurgence and to further control online discourse and media. The first half of the 2010s saw a quiet proliferation of these organisations, almost all with US/UK military/intelligence funding, pulling from Russia-hawk NATO academics, and building vast networks of uncritical propagandist journalists across the west.

To the degree that any of these groups had a public face, they were presented as 'anti-disinformation' organisations, focused on providing training to journalists and media figures. I practice they were a mechanism to build more formal international networks of friendly journalists to push US/UK deep state narratives and smear any opposing narrative as Russian disinformation. Journalists received payments, grants, training, exclusive access to state sources, and we're even provided a steady stream of stories in exchange for their work going after politicians, media figures, and other journalists deemed unfriendly to smear them as Russian assets.

Perhaps the most publicly famous of these groups (at least in the UK and Europe) was the Integrity Initiative. A subsidiary of the UK military funded Institute for Statecraft, it played a major role in smearing Corbyn's labour party, infiltrating a supposedly new independent left media including Novara (primarily via crank Paul Mason), but also interfering in the democratic affairs of multiple European countries including Norway, Moldova, and Greece, whilst building a broader smear campaign against most European 'left' parties as Russian assets or 'useful idiots'. It built a narrative, and a body of international 'journalistic' work that could reference each other as evidentiary despite all coming from the same secretive source, that anything from Asia-European diplomacy to unassailably factual documents planning the privatisation of the British NHS could be considered as a pro-Russian threat.

It was exposed in the UK through a combination of investigative journalism, email hacks released under the 'Anonymous' group name (which is meaningless as an identifier, but that's another issue), and a number of lawsuits here in the UK. Primarily though, Integrity Initiative overplayed it's hand as it went all in on destroying Corbyn and a resurgent left electoral movement. It's network of journalists were too eager to claim credit for their role thwarting this new threat in media party circles. Guardian journalist and II asset Carole Cadwalladr (who ironically was also at the centre of the Cambridge Analytica reporting which she used to burnish her credentials whilst simultaneously muddying that issue) overstepped in smearing conservative and Brexit donor Arron Banks as a Russian stooge, who then sued her for defamation where more information about II was made public in discovery. And critical independent journalists discovered that the organisation was supposedly an above-board Scottish charity, but it's registered address was a dilapidated water mill and many of its scarce registered details were either fraudulent or deeply suspicious.

Russiagate, shifting Brexit blame from the primarily US/UK/Saudi government and tech/social media dark money, and Ukraine war propaganda all came later and supercharged it, but the network for it had already been built. And it's had more than a decade to seed, grow, and expand. Further fuelled by what's now literal billions being spent by the US on countering 'foreign narrative threats' online, never mind the strategic placement of open intelligence assets at the top of every major social media company or publishing organisation under the guise of moderation and safeguarding. And that doesn't even take into account the wholesale capture of outliers like TikTok, first by Oracle and now by it's new private owners and IDF 'advisory' role.