Assad, from a Syrian Shiite people, drove all those Syrian Sunnis into Europe like cattle.
That affected the Brexit vote by a few percentage points.
In exchange, Putin gave Assad military support which saved Assad's regime.
Then the Russians launched a massive disinformation campaign about Brexit, that swayed the vote on Brexit one or two percentage points too.
https://www.theguardian.com/politics...-of-the-people
Vladimir Putin has said the UK should not hold a second referendum on Brexit, insisting Theresa May must “fulfil the will of the people”.