One decision that was/is very integral to their architecture is trying to copy how Docker handled registries and storage of blobs. Docker images have layers, so the registry could store one layer that is reused across multiple images, as one example.
Ollama did this too, but I'm unsure of why. I know the author used to work at Docker, but almost no data from weights can be shared in that way, so instead of just storing "$model-name.safetensor/.gguf" on disk, Ollama splits it up into blobs, has it's own index, and so on. For seemingly no gain except making it impossible to share weights between multiple applications.
I guess business-wise, it was easier for them to now make people use their "cloud models" so they earn money, because it's just another registry the local client connects to. But also means Ollama isn't just about running local models anymore, because that doesn't make them money, so all their focus now is on their cloud instead.
At least as a LM Studio, llama.cpp and vLLM user, I can have one directory with weights shared between all of them (granted the format of the weight works in all of them), and if I want to use Ollama, it of course can't use that same directory and will by default store things it's own way.
