How did L miss this?

There’s quite a few moments where it feels like characters are intentionally made dumb so that Light can prevail, but this is the most glaring one every time I rewatch. Light grabbed the Death Note. A minute later, Higuchi dies of a heart attack. How does L not notice Light killing him? “Oh hey Light, whatcha doing over there? Is that a hidden compartment watch? Are you writing something in there?”. L’s eyes should have been ON the Death Note and ON Light. Light committed a murder while the world’s greatest detective was sitting RIGHT NEXT TO HIM. Come on.

Even if L didn’t see Light writing anything down, nobody else could have killed Higuchi. Nobody else knew Higuchi just got busted, even if there was someone out there with a second notebook. If L had searched Light right after, he would have found the hidden note inside the watch. He’s L, the watch is like a party trick to him. He probably used one himself in the past. The others would have protested, but they wouldn’t have stopped him.

Higuchi died of a heart attack when Light held the note, and nobody else could have killed him. Even without concrete proof, that should have sealed the deal. And lack of proof didn’t stop L from restraining Light and Misa in the past.