Unlike search, Discover is intent-free: Google decides what a user might want to see. Content that performs well tends to be timely, engaging and visually rich, with high-quality images and compelling, non-clickbait titles. News, guides and lifestyle content often feature strongly.
You can't target a keyword for Discover, so the levers are indirect: strong E-E-A-T, large high-resolution images (enabled via markup), genuinely interesting angles, and consistent publishing in topics users follow. Being eligible also depends on meeting Google's content policies.
Discover traffic is powerful but volatile — a page can surge for a day then fade. Treat it as an upside on top of durable search traffic from evergreen content, not a channel you can fully control.