It's dumb, yes, but let it go. It's rap, it happens all the time
To play devil's advocate, do you think Pac would've dissed Biggie if Biggie wasn't the biggest rapper but just an aspiring emcee from around the way? Nope. There's no money in that. And it doesn't stop there.
Mobb Deep was starting to get popular when the "beef" occurred and they didn't even really directly diss Pac, but they still got a nice dedication in the outro of "Hit 'Em Up" along with some mentions in Runnin on E, When We Ride on Our Enemies, Why U Turn on Me, etc. Why? Because they were slowly getting popular, and there's money to be made when beefing with rising rappers.
I never heard of Chino XL until Pac dissed him. If anything, his simile was probably the worst thing anyone could say about Pac at the time (since he was hinting at the prison rape rumor), yet out of all songs (as far as most of us know) he just gets on line, while Mobb Deep gets verses and songs just for saying "Thug Life, we still livin' it." Why? Because Chino XL was a relative no-name, and there's no money in dissing him.
Nas had dropped one of the greatest hip-hop albums ever and was quite acclaimed. So yes, there would be money in dissing him about some obscure lines from It Was Written.
But if you look at the guys who ACTUALLY had something to do with Pac's sexual assault case and New York shooting, they never get mentioned until Against All Odds, yet Biggie gets songs and videos dissing him. Why? Not just because dissing guys like King Tut and Haitian Jack wouldn't be the smartest thing ever and may potentially put his life in danger, there's just no money in dissing someone who at the time not many rap listeners knew about.
Success in the rap industry has always revolved around what's hot at the moment... do a song with a hot rapper, you get radio play; diss a hot rapper, you get people's attention; diss a rising star, people start asking why and want to see what's next; etc. Hypothetically speaking, if 50 Cent dissed some no-name dipshit rapper who appeared once on 106 and Park's Freestyle Friday, would anyone care about it or dig deeper? Probably not. It's all about making that money, and 50 knows exactly how to do it, whether right or wrong, artistically creative or generic of the genre.