WI: The House of Luxemburg Survives?

My rough idea is as follows: Sigismund of Luxemburg and his wife, Marie of Anjou, produce a surviving son (basic POD being that the Queen of Hungary doesn’t die in childbed nor her stillborn son) to perpetuate the house of Luxemburg. The house of Luxemburg then survives for another century or so, but loses the Imperial diadem (to the Habsburgs or some other dynasty) for some reason half-way during the 15th century, whilst maintaining the Hungarian-Bohemian crowns.

The Hungarian and Bohemian crowns were in theory elective, but with the exception of Matyas Corvinus and Jiri of Podebrady, the crowns passed directly down the bloodline for the duration of the 15th century:

Sigmund of Luxemburg > Elisabeth (daughter) > Ladislas V (son) > Elisabeth (sister) > Ladislas VII (son) > Ludwik II (son) > Anna (sister)

Thus, I don’t think that the survival of the Luxemburg dynasty in the male line is completely unthinkable. Especially if they lose the Imperial crown for a similar reason to the Albertine Line of the Habsburgs (a candidate who is too young (even unborn) to succeed to the purple).

What effect will a continuous dynasty with clear cut heirs have on the kingdoms of Hungary and Bohemia? Will anything significant change with regard to them? Or will history plod along more-or-less on its OTL course?
 
It's exceedingly difficult to see how a surviving House of Luxemburg could lose the Imperial crown. The HRE Crown was basically de facto hereditary whenever there was a clear heir. Moreover Bohemia is an elector; there is little chance the Bohemian king would vote for a rival.

About the only thing I can think of is religion- if the Luxemburgs go Protestant (or Hussite) they could keep Bohemia and Hungary but lose Germany and the Empire. It would be a massI've clusterf*** though, TTLs Thirty Years War basically.
 
It's exceedingly difficult to see how a surviving House of Luxemburg could lose the Imperial crown. The HRE Crown was basically de facto hereditary whenever there was a clear heir. Moreover Bohemia is an elector; there is little chance the Bohemian king would vote for a rival.

About the only thing I can think of is religion- if the Luxemburgs go Protestant (or Hussite) they could keep Bohemia and Hungary but lose Germany and the Empire. It would be a massI've clusterf*** though, TTLs Thirty Years War basically.

Which is why I suggested a similar situation to Ladislaus the Posthumous losing the Imperial Crown, despite his dad being the King of the Germans (ie uncrowned/unconsecrated emperor). If the boy's too young or unborn at the time of his dad's demise, Bohemia and Hungary-Croatia will undergo a regency. The empire seems to want to avoid a regency wherever possible, hence why choosing Friedrich III (Albrecht's cousin) over baby Laszlo. I could see a similar thing happening with the Luxemburgs. Queen-Dowager left with an as yet unborn heir, the Regent of the Kingdom voting at the Imperial Election for someone else.

Or, the German electors simply decide they're tired of the Luxemburgs favoring Bohemia (and possibly Hungary) over themselves, so they decide to sidestep the issue and elect someone else. They gave Karl V an ultimatum that he wouldn't be able to pass the Imperial crown and the Spanish and the Burgundian one on to one person (and there the king of Bohemia was his brother).
 
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