Question: What dissolved the privileges in Poland of the empire that the British sided with against the Ottomans, the Kingdom that acquired some Thuringian territory in 1815, and the Habsburg Monarchy?

Passages:
If the British Empire was now going to side with the Russian Empire, the Ottoman Empire had no choice but to cultivate a relationship with the Austro-Hungarian Empire, which was supported by the German Empire. In a few years these alignments became the Triple Entente and the Triple Alliance (already formed in 1882), which were in part a cause of World War I. By its end in 1918 three empires were gone, a fourth was about to fall to revolution, and two more, the British and French, were forced to yield in revolutions started under the aegis of their own ideologies. Some reordering of the Thuringian states occurred during the German Mediatisation from 1795 to 1814, and the territory was included within the Napoleonic Confederation of the Rhine organized in 1806. The 1815 Congress of Vienna confirmed these changes and the Thuringian states' inclusion in the German Confederation; the Kingdom of Prussia also acquired some Thuringian territory and administered it within the Province of Saxony. The Thuringian duchies which became part of the German Empire in 1871 during the Prussian-led unification of Germany were Saxe-Weimar-Eisenach, Saxe-Meiningen, Saxe-Altenburg, Saxe-Coburg-Gotha, Schwarzburg-Sondershausen, Schwarzburg-Rudolstadt and the two principalities of Reuss Elder Line and Reuss Younger Line. In 1920, after World War I, these small states merged into one state, called Thuringia; only Saxe-Coburg voted to join Bavaria instead. Weimar became the new capital of Thuringia. The coat of arms of this new state was simpler than they had been previously. Poland's nobility were also more numerous than those of all other European countries, constituting some 10–12% of the total population of historic Polish–Lithuanian Commonwealth also some 10–12% among ethnic Poles on ethnic Polish lands (part of Commonwealth), but up to 25% of all Poles worldwide (szlachta could dispose more of resources to travels and/or conquering), while in some poorer regions (e.g., Mazowsze, the area centred on Warsaw) nearly 30%. However, according to  szlachta comprised around 8% of the total population in 1791 (up from 6.6% in the 16th century), and no more than 16% of the Roman Catholic (mostly ethnically Polish) population. It should be noted, though, that Polish szlachta usually incorporated most local nobility from the areas that were absorbed by Poland–Lithuania (Ruthenian boyars, Livonian nobles, etc.) By contrast, the nobilities of other European countries, except for Spain, amounted to a mere 1–3%, however the era of sovereign rules of Polish nobility ended earlier than in other countries (excluding France) yet in 1795 (see: Partitions of Poland), since then their legitimation and future fate depended on legislature and procedures of Russian Empire, Kingdom of Prussia or Habsburg Monarchy. Gradually their privileges were under further limitations to be completely dissolved by March Constitution of Poland in 1921.

Supporting sentences:
The 1815 Congress of Vienna confirmed these changes and the Thuringian states' inclusion in the German Confederation; the Kingdom of Prussia also acquired some Thuringian territory and administered it within the Province of Saxony. Gradually their privileges were under further limitations to be completely dissolved by March Constitution of Poland in 1921.