What is the meaning of [It is easy to be wise after the event]

When something has ended badly, it is easy to say what should have been done
to ensure success. Foresight is being wise before the event; being wise after
the event; being wise after the event is called ‘hindsight’. Many people are
gifted with hindsight – it is always 20/20!

> ‘If I’d been captian I should have put young Lawson on to bowl much earlier
and than we should have won’.
> ‘Bonnie Prince Charlie got as far as Derby and then retreated. If hadn’t
been persuaded not to march on to London he’d have become King of England.
What a lost opportunity! ‘
> ‘You went wrong when you…. . ‘
> ‘Why on earth he didn’t …. ‘
> ‘It sticks out a mile that instead of…. ‘