Why didn't L ever look at Light Yagami's Search history? Or why didn't the show ever address the fact that Light was looking up these criminals minutes before they died? That would trigger at least some sort of data traffic algorithm either set up by L or the Japanese government. So it seems to me that if any of these characters are as intelligent as the show makes them out to be they would've thought to look at his search history.
Don't tell me he probable cleared it or used an incognito tab because
- Even if he cleared it his IP is registered on all of the Wikipedia and news sites for the criminals he researched and
- They didn't state he used an incognito tab in the show so you can't assume that is the case.
- ALSO Incognito doesn't even stop you from being tracked completely.
I swear this entire show is resolved by looking at his computers footprint. Also Given L literally lives on a laptop in the beginning of his character development, you'd think he'd know enough about computers and web traffic to realize how easy it would be to find "Kira".