Boris Johnson received 92,153 votes in this contest.
The UK population is over 66 million.
At the 2017 general election the UK electorate had 46.8 million registered voters.
Boris Johnson became PM at the whim of approximately 0.139% of the UK population, or 0.196% of the voting population.
But please, continue to complain about how disgustingly un-democratic the EU is.