You just as likely to be right as wrong on that. The big problem with the intelligence community is they love to hide behind ambiguous obscurity. Drilling down to the originating actors of any clandestine action is extremely hard to be certain of. It's sometimes like a never ending onion, each layer just hides another layer.In my opinion, all the interest was from the US, getting the UK out from the EU, they knew what could happen in a few years (they were working on it) and the possible economic consequences. This way it was easier for them to take some measures (sanctions) at that moment that would affect the UK less (lol, it happened a lot otherwise). and so far everything has pointed to the manipulations of Cambridge Analytic
The one reason I feel there's a good chance that Russia had a hand in Brexit is due to this book.
The book actually states that in regards to the U.K. Russia should do everything it can to "cut it off from Europe". Then further considering that Putin is ex KGB and the author of the book is AFAIK part (or was) of Putin's inner circle it makes Russia look highly suspicious in regards to Brexit.