Because more people watched any Adam Sandler movie than people who watched Schindler’s List.
The majority of people, even if they’re not dumb dumb, prefer to watch easy movies at the end of a long day. And studio execs prefer to make more money than less.
There are studios that focus on smart and well done plots and movies, but that’s not what we’re talking about.
So you know how there's a superhero that is blind and orients himself via sound, and there's a superhero that doesn't have any superpowers and just goes against villains with the gadgets he made himself? One of them is named Batman, and the other is Daredevil
Light, guy on right - police chief's son, genius student with good grades and a tennis champion for extra curricular to get into a good school. Has ideas about what people should die for and what isn't being punished. Loses same sleep as guy on left, or so we assume, but hes a sociopath so the loss of sleep is more to do with thinking and less to do with fear or regret
L (just the letter), guy on the left - internationally recognized detective. Also genius. Also really good at Tennis.. I guess. It comes up once. Works with police and police chief to find the bad guy. Suspects Light, tells him so and his dad and enrolls in the same college. Does care about people, will make decisions where others are hurt if necessary but does clearly have morals. Weird dude, sits funny, likes sweets.
Light Yagami, one of my favourite characters. A single reason why is this; he looks unassuming as this description described. One of other reasons, he is just relatable.
You've had villain protagonist, and you've had relatable villain, but only in deathnote do you get relatable villain protagonist. Usually gotta read a century-old russian novel for that kind of stuff.