But generally, 'it all started' is a way of introducing a story that involves a number of factors.
'I've had a terrible day.'
'What went wrong?'
'Everything. It all started when I found I'd left my Bus Pass at home. So I had to pay, and the smallest I had was a fiver. Anyway, when I finally got to work there was a Post-It on my computer saying the boss wanted to speak to me a.s.a.p...[etc - a story of the whole day]... and when I got home I found I'd locked myself out, so I had to wait for you in the pouring rain.'
Student or Learner