Why is it der Finalist?

Finalist ends in -ist, and nouns ending in -ist are masculine: in a German dictionary, 97% of them take der.

All nouns ending in -ist
Sense 1
der

Meaning

[1] Participant in the final of a competition

[1] Teilnehmer im Finale eines Wettbewerbs

Examples

[1] "Elmar Mock, engineer of the Swatch clock and inventor or co-inventor of 178 patent families in 30 years, has been nominated as a finalist for the 2017 European Inventory Prize"

[1] „Elmar Mock, Ingenieur der Swatch-Uhr und Erfinder oder Miterfinder von 178 Patentfamilien in 30 Jahren, ist als Finalist für den Europäischen Erfinderpreis 2017 nominiert worden.“

Declension

1 Singular Plural
Nominativ der Finalist die Finalisten
Genitiv des Finalisten der Finalisten
Dativ dem Finalisten den Finalisten
Akkusativ den Finalisten die Finalisten

Pronunciation

Dictionary entries include material from Wiktionary. Wiktionary