We've expelled loads of Russians for spying, which includes blackmailing and bribing British politicians. Years ago, the Yanks tried to effectively mount a coup inside MI5 and grab control of it. And there was the plot to undermine and smear Harold Wilson, which was supposedly backed by Mountbatten. The NSA intercepted calls on Angela Merkel's mobile phone (and you can bet they did the same with others).
All major countries look to subvert or undermine politicians in other countries who they deem to be hostile to them. Masot's crime was getting stung and publicly shamed.