These lists are rarely from a single massive breach of a company like Valve (Steam) or Netflix. Instead, they are usually :
Premium accounts on these sites are frequently targeted for illegal resale or to bypass paywalls. 269k (STEAM,NETFLIX,HUBO,EPICGAMES,PORNHUB...)...
These are primary targets because accounts often contain expensive game libraries, rare in-game items (like Counter-Strike skins), and saved payment methods. These lists are rarely from a single massive
Credentials for these are often used to spread spam or phishing links to a user's contact list. How These Lists Are Created rare in-game items (like Counter-Strike skins)
"Infostealer" malware on a user's computer scrapes saved passwords from their browser. How to Protect Your Accounts