https://acoup.blog/2022/08/26/collections-why-no-roman-industrial-revolution/
Eventually in the 1800s, these engines get small enough and fuel efficient enough to be able to move their own fuel over water or rails, collapsing the prohibitive transportation costs that defined pre-industrial economies and in the process breaking the tyranny of the wagon equation, decisively transforming warfare in ways that would not be fully appreciated until 1914.
But the technology could not jump straight to railroads and steam ships because the first steam engines were nowhere near that powerful or efficient: creating steam engines that could drive trains and ships (and thus could move themselves) requires decades of development where existing technology and economic needs created very valuable niches for the technology at each stage. It is particularly remarkable here how much of these conditions are unique to Britain: it has to be coal, coal has to have massive economic demand (to create the demand for pumping water out of coal mines) and then there needs to be massive demand for spinning (so you need a huge textile export industry fueled both by domestic wool production and the cotton spoils of empire) and a device to manage the conversion of rotational energy into spun thread. I’ve left this bit out for space, but you also need a major incentive for the design of pressure-cylinders (which, in the event, was the demand for better siege cannon) because of how that dovetails with developing better cylinders for steam engines.
