so in the 15th century Matthias Corvinus, of the Hunyadi family ruled Hungary, Croatia, Bohemia, and for a few decades claimed the title Duke of Austria and resided in Vienna.
but Matthias's only son was rejected and the Ottoman trouble ended the Hunyadi dynasty (and the family's dream of becoming Holy Roman Emperor)
Matthais' only son, Janos Corvinus, was a bastard who was only 17 years old when his father died (in 1490). Janos was not in any position to succeed his father, and ended up as the ruler of Bosnia. He did well as ruler of Bosnia, and had a few children who were lost to history.
but what if the Ottomans did not attack Hungary, so Hungary dominated Austria....
could this have led to Hungary entering the HRE, becoming an elector or even Emperor?
and what other effects would there be from a Hungary-dominated Austria?
The Ottomans destroyed Hungary at the Battle of Mohacs. This was decades after the Corvinus dynasty was gone.
I don't think that Matthais wanted to be HRE. His strategy of expansion west was so that he controlled more stable territory so that he could fight the Ottomans. He needed the territory for security.
If he lived, then he actually might give his Austrian territory back to the Hapsburgs, in exchange for Frederick III, the Hapsburg HRE, recognizing the bastard Janos Corvinus as the Crown Prince of Hungary. With this recognition then Janos can get a bride, Matthais seemed to be looking to Italy (wikipedia mentions Bianca of Milan, Il Moro's neice and OTL wife of HRE Maximilian I). Let's say Matthais lives 10 more years. He dies in 1500. Janos is 27 years old and has a son. He commands his father's army and is recognized as Matthais' successor.
If Janos is able to become King and rule as his father did (which is the only way that he would be able to become King) then I think that Eastern Europe would see the establishment of a strong Hungarian state. Matthais had tamed the Hungarian nobility, if only temporary. Janos could continue the trend.
A strong Hungarian Kingdom does not get destroyed at Mohacs (the Battle probably doesn't even happen since the European politics that caused it would change to much).
