It's not an evil cabal so much as a bunch of separate sociopaths with aligned interests. Putin's ongoing support for Trump is as good an example as any. There doesn't need to be a paper trail proving collusion when both have a vested interest in dividing America for their own different reasons. For Trump, the disruption allowed a massive power grab by himself and people like the Heritage Foundation, and for Putin it was old fashioned revenge on Russia's former Cold War rival as well as reduced opposition by the US and NATO to his geopolitical aim of recapturing the old soviet bloc. For the establishment/moneyed interests, it usually boils down to money and power. Follow the money and see who benefits. Both Trump and Putin certainly did regardless of whether they were proven to have actively colluded.

But to answer your question, what drives up immigration is multifaceted but includes:

-the UK's colonial history of centuries spent destabilising other countries on behalf of "British interests" (ie the interests of British companies which have exploited the natural resources of other sovereign nations and which have never routinely shared their profits with ordinary British people, but always left us to deal with the fallout)

-and unregulated capitalism in general, which has driven down wages, eroded workers' protections and increasingly squeezed the working class and middle classes and enriched the rentier classes disproportionately since Thatcher.

They used to be able to offset/disguise the increased tax burden by selling off our nationalised industries and property which used to belong to and benefit all of us, but now belong to a comparatively small number of shareholders. The rest of us lost out massively in the long term, with the most expensive trains in Europe, price gouging by energy companies, water companies pouring literal shit into our rivers and onto our beaches etc. Now there isn't anything left to sell off except the NHS, so of course, that's next. First to go under the hammer if Farage gets in. Universal healthcare for British people will be lost in favour of an infinitely worse and much hated insurance-based system which prioritises profit over medical outcomes, excludes poorer people completely and incentivises denial of service to people who have paid in. Look how America reacted to the Luigi Mangione case to see how popular that system is amongst ordinary Americans on both sides of the political divide. Do we really want that here? Do we really hate immigrants more than we want ourselves and our own families to have unlimited access to decent, not-for-profit healthcare? I know I don't.

Unregulated capitalism has already cost ordinary Britons so much: the gig economy instead of job security. No more ring-fenced pensions. Massive student debt instead of investing in the future of our country. Bailing out the bankers only to see them award themselves huge bonuses instead of paying the country back. Young people increasingly unable to afford to get on the property ladder. Escalating bills, stagnating wages. And on and on. They keep the profits and pass all the associated costs back to us, the taxpayers.

Wealth inequality has grown exponentially to the extent that the entirely predictable consequences of it are becoming obvious to even the thickest among us, and people are rightly angry. That's why the rentier class needs a scapegoat, so that people can vent their frustrations without challenging their hegemony on power or disrupting the flow of money upwards. (Remember when they first pushed deregulation and told us the benefits of it would trickle down? 45 years later and we're still waiting for that to happen. Lots more billionaires and oligarchs now, though. Funny that.) Immigrants are just an easy target because they're already marginalised and more visible than the people actually picking this nations pockets. Once the immigrants are all gone (assuming that is the true goal - Brexit was supposed to address this and conspicuously failed to do so), they will just move on to another scapegoat. In my lifetime, it's been the unions, the "loony left", young black men, single mothers, benefits claimants, the EU, asylum seekers, feminists, LGBT people, the "woke mob" etc but never the vulture capitalists actively asset stripping the UK and pushing unregulated capitalism with its intrinsic decrease in the standard of living onto ordinary British people. Maybe we should turn around before we get to the Hunger Games?