There's plenty of old buildings here that are not built up to the latest standards; increasing exponentially the further you get from the core of a big city.
Japan is _very good_ at tearing down old buildings and building better in their place; but it doesn't mean that there are zero old buildings around.
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.
Like half of the buildings are non-resistant since they are old and made of wood. IIRC only buildings built after 1991 are guaranteed to be earthquake resistant.
Yes, but the situation got a lot better and a lot worse...
Sadly there has been a bunch of pretty devastating earthquakes in recent years.
In particular in Kumamoto the one in 2016 (magnitude 6.5) was huge and many of the houses built at lower standard or not in great shape anymore got partially or totally wrecked. Right now the house that are left are relatively well built.
The bad news is, that still doesn't help as the cumulative damage can still bring them down, and they're still subject to landslides, water damage, and other second order disastrous events.
Which works great in earthquakes in my experience in Christchurch. Most homes in New Zealand are made of wood.
Christchurch had a 7.1 that was 40km away, that caused some damage (certainly the wooden house I was living in at the time was fine).
Christchurch then had a 6.2 which damaged many concrete and brick buildings because the epicentre was shallow and within the city (6.2 sounds small but if it is close then that really matters). Many house foundations were completely stuffed, but the wooden houses above were often relatively unscathed. I bought a damaged house cheaply with a broken ring foundation: "as-is" or uninsured or insurance payout are the keywords.
Christchurch had maybe 180000 homes, of which about 10,000 were ultimately demolished. But they mostly weren't demolished because the wooden home itself had failed. The majority of demolished homes were in red-zones beside the river or estuary, which the houses could have been repaired but the ground was not good and also future flood risk was the problem. The government, the city, and insurers worked together to remove a lot of homes that had other risks.
For a long time "live with earthquakes and build accordingly" meant "make it easy to rebuild", not "engineer the structures to withstand the earthquakes".
The regulations got hardened in 1991. Obviously there has been earthquakes forever, but the buildings were not built to withstand them. That's one of the reasons why Japanese do not buy old homes: they are not earthquake proof.
One of the reasons Japan uses wood for construction is that combined with their traditional building techniques it results in earthquake resistant buildings.
Japan is _very good_ at tearing down old buildings and building better in their place; but it doesn't mean that there are zero old buildings around.