Because just inflated muscles don't do these? The gap between the two is not that big, the body-builders just go a bit less intense on the heavy lifts in order to have some energy left for the isolation ones, and the rep range being higher makes the weights 20-40% smaller. The difference between 5x5 150kg bench presses vs. 5x8 110 kg ones + doing pec-decs is nowhere nearly as big as the difference between these two and just about anything else. The primary difference is joints and ability to move heavy objects. Doing more in the sense of being more a of human forklift somehow does not look that glorious. The feeling better may as well attach better to the more spectacular looks, and as for longer lasting, probably near draw.

For me strength always meant punching strength and this guy convinced me it is mainly technique.

Caveat: I know grappling sports are getting more popular, such as BJJ / part of MMA. I think this probably does not apply there. I think grappling could be more brute-forced.

I think one reason modern culture may be hooked on strength is that when we were children a lot of fighting / domination / bullying / rough play relied more on intuitive grappling than on punching (or kicking). This made us all respect The Strong Guy Who Can Whip Everybody. And of course movies like the 300 etc. reinforce it. This goes back to very old cultural origins, wrestling is one thing many cultures paralelly evolved because this is how people can physically dominate each other and establish a pecking order without actually hurting each other.

Here is why I like to argue it: weight lifting techniques are used in many sports for a long time. Still, most guys were scrawny, and not due to lack of nutrition, since even today some lifters use really easy nutrition like eating lots of cottage cheese. Or drinking lots of milk if they are tolerant. Body building got popular in the West roughly after 1977 (Pumping Iron) and elsewhere later, I would say, buff guys on bar dancefloors became a common sight 1990-ish, roughly? What do you think body building brought to the table that former lifting couldn't? I think it brought ease through isolation. That while doing the triceps cables is straining for that muscle, it is not straining for the rest of the body, nor the mind. You can almost not pay attention, and not even feel tired, just stop it when the muscle itself burns but you can almost even avoid getting sweaty. This ease brought a strong motivating factor. When I was 17 it felt like a cheat code: I was sitting in the 45 degree leg press, and wondering how amazing it is that I am sitting on my ass, laid back, relaxed, yet got better looking legs that classmates who played soccer all the time.

The current SS / SL 5x5 trend is bringing back the former, pre-body-building era, where your energy is wasted on making sure your posture is right, all the secondary muscles are flexed all right and so on. While with a 45 degree leg press basically the only tiring, attention-grabbing, willpower-sapping activitiy is just pressing the legs up, with a squat you must pay attention to getting the whole body right, which is much more tiresome hence demotivating, because most of that does not apply to good looks, just a rather useless forklift-ability.