I think your comment is closest to reality. I believe it was incremental and deliberate, but the key piece that is missing from your assessment is that we (the royal "we") haven't given a lot of attention to correcting any poor choices. I think you are right when you say that hardware improvements helped encourage devs to give more tasks to the machine like encoding, caching, etc. However, it also became less important to revisit the underlying pieces on top of which we added these new features. It eventually became this dirty snowball rolling downhill that was built from layers of whatever was in the way as well as anything we could throw at it.

For example, the web might be filled with redundant and bloated software, but the real problem is that the browser has become the nexus of virtualization, isolation, security, etc. for almost everyone from the causal user to hardcore admins and for every piece of software from frameworks/utilities to full-blown SAPs. It's like we have all reached a common understanding for what comprises a "good" application, but then we lazily decided to just implement these things inside another app. I mean, webassembly is great an all, but is it wise?

I don't think it's about IPC or RAM or (n+1) framework layers that each include "efficient list functions". I think it about the incremental, deliberate, and fallacy-laden decisions that assign more value to "new" than to "improved".