Yes, but it wasn't invented from nothing in 2017. Soft attention existed in other applications like information retrieval, Nonlocal networks had similar ideas as well. But it wasn't seen or used as a fundamental building block. But it wasn't something out of the blue either.
I suspect it was considered many times, but the sheer computation scale would make it feel like obscene brute force. It feels like the right shape but too wild to think about implementing.
I think as time went on, and hardware got better, it seemed more reasonable to actually think about a viable implementation of what I think was a widespread intuition anyone in ML had that everything's context is everything.
It just seemed like a theoretical thing until hardware caught up. Maybe. Perhaps I'm applying a retrospective excuse to why it took so long.
People definitely wanted to train deep networks before, but didn't know how. They evdn tried things like training layers independently.
I don't think it was intuitive to anyone back then, the vanishing gradient problem was a big deal since the dawn of NNs. I'm not sure what you mean by sheer computation, residuals allow you to have deep networks instead of shallow and wide ones. You can have equivalent parameter count.
Like the best leaps in thinking, once it is made, is is immediately obvious and intuitive.