"Vì lợi ích của mọi người!"

"For everyone's benefit" should be accepted.

Thank you Duolingo for creating this Vietnamese course for the benefit of everyone wanting to learn :)

From Chinese 利益

• Mandarin: lìyì
• Cantonese: leihyīk

If you add a modifying phrase to "everyone" as in "everyone wanting to learn," you, of course have to say, "for the benefit of everyone." Without the phrase, "Thank you , Duolingo, for creating this Vietnamese course for everyone's benefit," works naturally. The point is that the phrase in isolation is also correctly translated, "for everyone's benefit."