These days, unfortunately, there are very few politicians anywhere who have not been caught out telling lies.
Or saying one thing before they are elected and doing the opposite after coming to power, which I find just as dishonest and despicable.
Some people genuinely like and believe in Johnson (yes, I know that is hard to believe, but some GENUINELY like Trump too!)
Others probably never listen very carefully to what a politician says, so they don't notice that he is lying, and certainly do not remember his previous words when later someone says, or even proves, that they were untruthful.
I have often wondered how this situation can be remedied, but I don't have a solution.
In private life too, I find people lie more often now than they did formerly and no-one takes them up on it either.
Perhaps that is where we need to start - confronting those who lie to us and sharpening awareness of the difference between the truth and a lie.