Linus is one of the OGs and a lot of people get introduced to PC building through him and then move on to the mentioned channels. He's good at explaining the basics in an understandable ways for beginners and still has some nice content others can't really pull off because he is so big and influential.
If you only do gaming, go for an i5 i guess. But if you do alot of multitasking such as gaming and streaming or editing videos, the 3700x will completely destroy the i5 in performance. The i5 also uses twice as much power as a 3700x