There is a chicken-and-egg problem for the ammonia economy.
As you stated there are many current uses for Ammonia.
The core problem is getting the price of green Ammonia lower than Ammonia production that vents the CO2, so that market mechanisms can kick in.
The main solution is likely regulatory. Carbon (border) taxes on the alternative, incentives for green hydrogen production, ever increasing quotas for percentage of green Ammonia produced and consumed, corporations trying to hit decarbonisation goals etc.
It's not so much an implicit expectation as a explicit forward plan by the same parties who are buying up cattle stations next to the mines they own | operate to generate power and ammonia for their own ends.