Why did Dalmatian become extinct?

The extinction of the Dalmatian language was a gradual process driven by the language being replaced by other tongues in the region. It is likely that, outside of isolated pockets, Dalmatian was superseded by Croatian and, to a lesser extent, by Venetian, a dialect of Italian.1

The language's decline occurred over several centuries, with the Ragusan dialect disappearing by the 17th century. The final dialect, Vegliot, survived until the 19th century; its last known speaker, Tuone Udaina, died in 1898 after being killed by a land mine. Because Udaina was not a native speaker and had not used the language for decades, his death marked the definitive end of the language as a living, spoken variety.21