I Blame Communism
Banned
An "all-Slavic" crown would be dysfunctional. Logistically, it would be absurd, and its inhabitants would quarrel ceaselessly. The Poles and Ukrainians were managing to haise rooves within the city limits of Lviv. Poles had sabotaged the united Czech programme in Hapsburg Silesia, and we all know the love-fest that goes on between Serbs and Croats.
Ideas of "Triple Monarchy" were always based on either Czechia or Croatia, not both. First it was the Czechs, who had a sense after 1867 that the Magyars and Poles, the other victims of '48, were having it all their way (whereas the Croats hadn't suffered from '48 in the same way, and weren't too hostile to the new 1868 settlement).
The constitutional crisis which was provoked by ( if I may be permitted my habitual Czech bias
) the absurd stubborness of the Sudeten Germans even called the full sovereignty of the monarchy into question (Bismarck expressed concern at "the marginalisation of the empire's Germans" which suggested the Reich had a license to look after Volksdeutsch interests in other countries). Hence, later attempts to add a "third leg", which were based firstly on sticking it to Budapest and only secondly on the aspirations of the Slavs, ignored the vexed Czech question and settled on uncontroversial Croatia. The Slovenes, famous for being the only entirely inoffensive people in the Balkans, were sort of dragged along: the Illyrian Movement and later the National Right Party in Croatia tended to consider them Croats who lived in the mountains like a bunch of Germans; the Germans likewise to be Germans who talked funny, like Croats.
Ideas of "Triple Monarchy" were always based on either Czechia or Croatia, not both. First it was the Czechs, who had a sense after 1867 that the Magyars and Poles, the other victims of '48, were having it all their way (whereas the Croats hadn't suffered from '48 in the same way, and weren't too hostile to the new 1868 settlement).
The constitutional crisis which was provoked by ( if I may be permitted my habitual Czech bias