Yes they did, though the influence those bots and St Petersburg troll farms had on Brexit and the election of Trump may not have been decisive. Since then, they have also fanned the flames of the Pizzagate and QAnon conspiracy theories.
I have already posted a shedload of links to articles about some of this on page 142 of this thread.
For book length treatments, see Yale historian Tim Snyder’s The Road to Unfreedom, Peter Pomerantsev’s This Is Not Propaganda, and Mia Bloom and Sophia Moskalenko’s recent book on QAnon for that particular angle. It’s actually backfired on the Russians a bit as QAnon has now acquired a following in that part of the world too.
Will leave it there as I don’t want to take this thread off topic and am aware that a lot of people were perfectly capable of voting ‘Leave’ without having fallen prey to the malign influence of the ‘Internet Research Agency’.