I wonder if all the instructional content on Youtube makes training with weights and weight machines more accessible than ever. I was intimidated by weights and figured it would be boring. A guy I knew was talking about his weight training and I asked if he plans things out with friends/workout buddies and he said he learns about it on YouTube. So when I finally pushed myself to try weights, I found a video. It was a petite woman (I'm a dude) and I thought, ok she looks better than I do and this routine is a nice start. And I went from there, in my forties.
My funniest theory is that dating has been getting more competitive and strength-training is good for confidence.
You are right, but the reason it's so prevalent is also because it is better for capitalism. Going to the gym isn't just a 1-off activity, it's an entire lifestyle & it doesn't necessarily come cheap. You need a membership, specialized gear, lessons, switch your consumption habits to high protein foods ... etc
You might be overthinking this, although I understand how it can appear that way for someone on the outside looking in. Your local gym probably costs less than your Netflix subscription, if you don't already have a free gym in your apartment building. You don't really need anything else other than looking up some routines on reddit.