They could have been further away from the epicenter of the previous ones, or the previous ones weren't strong enough to cause that specific structure to collapse, the previous ones might have weakened the structure and this one brought it down, a million different things factor into this.
Earthquakes aren't a perfectly repeatable occurrences you can run a regression test against.
Meanwhile here an 80 year old, completely unremarkable house is likely to get declared "historic" and you as the owner can't even change the windows without permission. Tearing it down would be virtually impossible.
Some of those old houses seem to burn mysteriously. Bad wiring, I suppose.
Then there was the developer who tore down a couple of houses over a weekend before the historical commission had a chance to meet and formally confer historic status on the rotting, worn out properties.
Earthquakes aren't a perfectly repeatable occurrences you can run a regression test against.