I think this is all rooted in one thing; the marriage of actress Grace Kelly to Rainier of Monaco, which is a 'tiny principality' (like, a square mile), filled with duck all but casinos, foreign tax exiles and yachts, and her story is seen as a real life fulfilment of all the Disney versions of Hans Christian Anderson's tales about commoners or hidden royalty marrying princes.
I'm not sure people who lap this Hallmark tit up even understand the difference between constitutional and absolute monarchies. But this fantasy being fixed on modern European absolute monarchs is weird, because there's not even a single absolute monarchy left in Europe unless you count Vatican City, and you can't marry the Pope. Other than that, there are only a handful left in the entire world, most of them being Muslim states where the King (or Emir, or Sultan) can have multiple wives - Saudi Arabia, Brunei, Oman and I think UAE counts, then there's Swaziland in southern Africa, where the king also has multiple wives, I think at last count 15, and which is basically famous for being poor and being devastated by AIDS. Not sure any of this fits the Hallmark fantasy! I mean, another beautiful US movie star - Rita Hayworth - married an esteemed and filthy rich Muslim son of a spiritual leader and a Prince - the Aga Khan's son Prince Aly Khan - but that one doesn't seem to have captured the imagination the same way. Partly because it was really unhappy and they divorced quickly, but eh.
Which is again weird because all Europe's remaining monarchies exist in functioning democracies and most of them already marry non-royals these days, and people who have had *gasp* jobs!