you clearly don’t know the history of disinformation/propaganda campaigns/operations the soviets did through out the 20th. they are absolute masters of such matters.

Russians and Russia are not Soviets and USSR: there are too many differences in terms of resources, ideology and motivation. You can't make people do something with any amount of propaganda if they don't feel the need to do it, the best you can do is making them apathetic about things you don't like by discrediting it but it requires a multi year effort of constant 24/7 brainwashing similar to what they did in Russia and USSR. Nothing like that could even remotely be possible in Brexit or Trump cases, especially with very modest propaganda resource Russians have.

Most of KGB successes (independence movements in colonies, left-wing parties, etc) were a result of support of an existing movement that already had significant popular support even before KGB involvement. That is all they could do or any other intelligence agency could do: you can't brainwash people into anything unless they already want what you want unless you indoctrinate them daily for many years which is only possible in homeland and even that has a lot of limitations.

Putin's past isn't relevant at all because his KGB job was insignificant in terms of his influence in KGB. It is only interesting because it explains a lot about his personality and way of thinking, but nothing else.