Dumb Question: Why was Maria Luise's Marriage to Napoléon Never Annulled?

[Kellan Sullivan]

After Napoléon fell, no one had ANY intention of his wife joining him on either Elba or St. Helena. Yet the pretense of the marriage was still maintained until Nappy's death.

Could Franz II have induced her to agree to an annulment? (On what grounds? Usual chestnuts of consanguinity and non-consummation would be off the table). It would bastardize Reichstadt (probably, since I can't see Franz petitioning for a separate dispensation confirming the boy's legitimacy), which means the Bourbons would likely sleep a bit easier (although Reichstadt's bastardy might be regarded by some like Mary Tudor's was earlier). Plus it would allow Franz II to remarry his eldest daughter advantageously (duke of Modena maybe - can't think of anyone else) in Austrian interests. I've read he was fine with his daughter's relationship with Neipperg (despite it being beneath her) because it kept her from Napoléon and her son. But in theory, wedding Luise to almost anyone else would achieve the same goals, wouldn't it?

 

[Kellan Sullivan]

Let's look for bridegrooms:

So, the duke of Modena was married by 1812, which makes him an unlikely candidate for Maria Luise to remarry to.
Kings of Naples and Sardinia were both married.
The grand duke of Tuscany was a widower who only remarried in 1821. (but he's also Luise's uncle, so while the Habsburgs did this type of thing, I don't think Franz II would be interested in having his grandkids only be able to inherit if his nephew dies.
The duke of Parma might work - albeit he's eight years younger than Luise. Which basically rules out Italy.

Fernando VII of Spain only remarried in 1816, so Franz II might think a double Iberian suit (Luise to Fernando and Leopoldina to Pedro) might do nicely. His second wife died in 1818, if the annulment's not ready by then (although OTL Luise has had three of her four kids by 1818).
The Bourbons in France wouldn't be interested - although for sheer hilarity, I would pay to see Franz II annul Luise's marriage to Napoléon and marry her to the duc de Berri. The Bourbon line was running low on boys, they needed a match sooner rather than later, with a girl who was known to be fertile.
Ludwig I of Bavaria's married since 1810, but his only brother married morganatically in 1823.
The future king of Saxony is too young for Luise (besides, Saxony was on the losing side, you don't still want to reward them)