Why is it der Erpresser?

Erpresser ends in -er, and most nouns ending in -er are masculine: in a German dictionary, 86% of them take der.

All nouns ending in -er
Sense 1
der

Meaning

[1] Person who puts others under pressure and forces them to do something

[1] Person, die andere unter Druck setzt und sie zu etwas zwingt

Examples

[1] The extortionist demanded ten thousand euros

[1] Der Erpresser forderte zehntausend Euro.

Declension

1 Singular Plural
Nominativ der Erpresser die Erpresser
Genitiv des Erpressers der Erpresser
Dativ dem Erpresser den Erpressern
Akkusativ den Erpresser die Erpresser

Pronunciation

Dictionary entries include material from Wiktionary. Wiktionary