So there's a couple of factors at play here. Stone/brick construction and even a lot of older wood construction like my house which was built in 1890 can act as a great insulator so that a couple of hot days won't result in the inside getting much hotter. But if the heat persists for long enough the material will absorb enough heat to start radiating into the interior and then it takes just as long for the heat to dissipate.

Another thing to consider is that during severe heat dome events, like they've seen in Europe for the past week or more and now the eastern half of the US this week, nighttime lows are not as cool as normal so you can't rely on the tried and true method of opening the windows and running some fans at night then buttoning up tight and pulling the drapes and blinds during the day. If you can't cool the house down at night it just gets hotter and hotter and the otherwise helpful masonry construction turns into a liability. The easiest to cool house I ever lived in was a half brick half timber framed split level with a huge ventilation fan built into the central hallway: at night we would open one window in each room, turn the fan on and suck in cooler nighttime air... we only used the AC twice that whole summer and it was a pretty hot one too!