The Savoys are on the fringes of the royal society in Europe. It’s unreasonable to expect the reigning families to attend a funeral of a private citizen with whom they have very little contact.
Good to see the old Queen of Spain present though.
The royal houses that chose to ignore the funeral were mostly the Protestant ones (the British, the Dutch, the Scandinavian, and the non-Catholic German houses) although there were some missing Catholic families (Bavaria, Belgium, Liechtenstein) and Orthodox families (Romania) too.
The extensive guestlist, however, seems to indicate that the Savoys are not exactly "on the fringes of royal society" in Europe and, moreover, it was an implicit recognition of Emanuele Filiberto as the new head of the House, at least by the royal houses that were in attendance, not to mention obviously by the Roman Catholic Church, which is the most important endorsement in Italy.
Actually these can be positive times for the main branch of the Savoys. Emanuele Filiberto is (was?) a bit of a playboy, but he is well-known, possibly even a celebrity, in Italy. I believe that he and his gorgeous young daughters have the potential to become very popular with younger generations of Italians. That doesn't mean a restoration of the monarchy, or that anyone will seriously consider them for any semi-official state role as the Royal House of Romania has apparently managed to secure for example, but hopefully there will be a "normalization" of the relations between the Italian Republic and the House of Savoy, more along the lines of what we see in Portugal, maybe even in Austria or in France, where the Royal Family is respected as part of the heritage of the country.
Of course I don't expect either that the Italian Republic will return the Quirinale Palace or Villa Ada to the Savoys, as Vittorio Emanuele once (somewhat delusionally) demanded, but they may make some progress getting back their family jewels for example, which I sincerely hope. Punishments cannot carry over from one generation to another in the same family. That is wrong.
