I can not find any source that many thousands if not tens of thousands died in Europe in 2019 from the heat wave. Can you point me to your information source? I believe you are confusing the 2003 heatwave from over a decade ago with the one in 2019.

The 2019 heat was directly implicated in the deaths of at least 15 people. Five died in France, four in Germany, three in the United Kingdom, two in Spain, and one in Italy. Nine of these were drownings, attributed to people cooling down, and another involved an exhausted farm worker who went unconscious after diving into a pool. The three who died in hot air were aged 72, 80 and 93. Approximately 321 million people were otherwise affected by similar temperatures in the same countries.[1]

[1]https://en.wikipedia.org/wiki/June_2019_European_heat_wave

Edited for clarity