Why does my mascara keep smudging even though I applied it?

When I put in the effort to even apply mascara in the morning, I definitely looked fine at home.
But there are so many days when the area under my eyes gets slightly dark after a few hours of being out.
It feels like it gets worse, especially when I smile or as time passes and oil rises, so it bothers me every time I look in the mirror.
I thought it would be fine since it was a waterproof product, but it turned out that even that wasn't completely smudge-proof.
It's fine on some days, but it spreads particularly badly on others, which makes it even more confusing.
I hear a lot of talk about applying powder under my eyes and using a setting spray before mascara, so I don't know what to change first.
I've seen comments saying that longer eyelashes smudge more easily, so I'm curious if that really has an effect.
I think I check under my eyes more often, especially in the summer or on humid days.
It’s stressful when I’ve put in a lot of effort to make my makeup look neat, but it ends up looking messy just because of the mascara.
So these days, finding a smudge-proof mascara has become a more important concern.
I'm really curious what combination everyone uses to prevent mascara from smudging.