Could someone explain to me what Lord Keynes *meant* by “The inevitable never happens. It is the unexpected always.”?

Was Keynes being sarcastic, or was he being serious? Is the remark a display of his wit or his witlessness? I honestly can’t tell.

Was Keynes saying, for instance, that no matter how inevitable an outcome is, you can always find someone surprised by it? Or is he the one surprised by the inevitable?

I, too, find the quote memorable. Only I’m not sure why!