Nothing is going to stay in some fixed microcosm when it is projected to grow. Satoshi himself said that Bitcoin was going to be big or nothing, so there was no vision that Bitcoin would remain some niche experiment as it, of course, had to start out small before it could become bigger.
Again: once, while discussing future user base growth, Satoshi considered 20% per year (doubling every 4 years) a "crazy" rate of growth. That would be consistent with his chosen block reward schedule (halving every four years). With a "non-crazy" growth rate of less than 20%/year, the USD value of the block reward would have deceased with time, forcing the system to transition gradually to fees.
Surely he was too smart to risk actual predictions, but on the other hand he cannot have expected the price to rise by a factor of 10 every year for 5 years. So the USD value of the block reward too
increased by almost he same factor, instead of decreasing as he may have expected.
The price rose so fast because of speculative investment and trading, fueled by predictions that it would one day replace VISA. That surely is a use for bitcoin that he did not expect. If there is something that the world did not need in 2009, and will never need, is another penny stock. He would not have bothered creating bitcoin, if he knew that it would turn into that.