With the charisma of wilted spinach, which is why he had no impact.
I agree he is a good person, but he was not an effective leader. You don't need to be a Lord Flasheart-type like Boris - Angela Merkel was a very different type of leader (thank god) and highly successful - but you need that undefinable something that effective leaders have.
Basically, if you can't imagine the person persuading a roomful of people to do something they don't want to do, that person is not going to succeed as PM.
If I wanted someone to look after my cat, I'd choose Farron, or May, or Sunak, over Johnson, who would probably lose the cat and/or shag it. However, as much as I despise Boris, if my back was against the wall, and I needed someone to persuade my team to go over the top into gunfire, metaphorically or actually (in the WW1 sense), I would choose Boris over Sunak or May, every time.