So What DID Happen In 1540?

Europe's hot, super hot and about to get hotter and you can't pick up a newspaper or hear a weather report without reading or hearing how we are about to be hit by Europe’s worst heatwave since 1540, since Henry VIII was king, and while this heatwave in 2022 can be laid squarely at the feet of man made climate change, what happened 582 years ago when climate change was not an issue?
The simple answer is that for eleven months it just didn't rain much in Europe leading to a mega-drought which resulted in half a million deaths across Europe as forests across the continent went up in flames, smoke darkened the sun, wells and springs dried up which all combined to push temperatures way above the normal values and in many places, temperatures exceeding 40°C.  
The smoke acted in much the same was as Greenhouse gases do today, albeit in 1540 it was temporary and eventually cleared which won't happen in 2022 but the lack of rain which kick started the drought came about due to something called soil desiccation feedback.
Relying completely on scientists for this bit, it appears that drought-induced cracking of soils disrupts the water evaporation process so less goes into the atmosphere so less going up means less to come down as rain so even more soil desiccation and so on.
All very informative but still doesn't answer my question of what happened in 1540 to cause the drought which led to the soil desiccation which pushed up the temperatures which caused the fires which blanketed Europe.   
I couldn't find any major volcanic eruptions in 1540 or Solar Flares or anything which could explain what sparked it off so we know the result but frustratingly not the initial cause of the 1540 heatwave and wow that's annoying.