Death Note and Attack on Titan's successes as manga are only part of why they have gone on to become well-received mainstream anime adaptations. The other secret to their success? Tetsuro Araki, their director.
Digibro eloquently argues what it is about Araki's style that sets anime like Death Note and Attack on Titan apart. For one thing, the director excels at making bombastic anime. I don't mean in a Michael Bay way. Rather, Araki is more like Zack Snyder when it comes to directing anime. Araki can even make mundane things like writing in a notebook seem dramatic and enticing -- nevermind when it comes to the extreme emotions displayed in Attack on Titan. There, Araki is capable of making speeches seem like the most intense thing. It's a style that has allowed Araki to create some of the most memorable scenes in anime, ever. Couple this with interesting themes, and it's no wonder that both Attack and Titan and Death Note are so hot, even with audiences that don't normally watch anime.
Digibro also dives into other anime that Araki has directed, analysing the different strengths that each showcases. It's a fascinating analysis that's worth your time, if you have nine minutes to spare.