Now my theory, and it's just as valid as yours, is that Butterfly is bollocks. History is like a big pond. If you throw in a pebble it makes a splash, and there are ripples, which spread out and become less an less as they go further and further. A little pebble has hardly any effect, a big rock disturbs the whole pond for several moments but eventually, a placid surface returns, and history proceeds, just as before.