Hah, well what was the rate of progress on breeding faster horses vs. internal combustion in the late 19th century? I don't imagine that the progress rate was very high for horses..
I'm not so sure about internal combustion, but I think it took steam engines 100 years to start outperforming horses.
I think that that's a better technology comparison because internal combustion was able to leverage the theoretical insights originally derived for steam. There's no shoulders-of-giants effect going on for nuclear fusion, as there wasn't for steam.
Well, it kind of depends on what you define as teh first steam engines. Are you including like novelty stuff used for entertainment like magic shows and fountains? Or are we starting with the first steam engine used to do real mechanical work? The Newcomen engine came out in around 1712, but it's initial purpose as a water pump for mines wasn't really in direct competition to horse powered pumps. While they could be used to generate power for factories, that was an uncommon use case because they gradually lost power output over time.
The Watt design is when we finally saw steam engines replace animal power in the late 1770s. So not quite 100 years.
But yes, ICE development benefited from all the problems solved by steam power generation. I believe the ability to machine pistons to an accuracy of 0.1" wasn't developed until around 1750. Prior to that, people just hammered iron roundish and called it a day. Good enough for large steam engines, but not too valuable with an ICE.
Long term projects often have the problem they are solving disappear out from under them. They become obsolete before they're done. Freeman Dyson famously pointed this out and suggested anyone planning ahead more than five years was fooling themselves (and he meant that in science, too.)
Fusion seems a good illustration of this. Work started on it about half a century ago. Its motivation was "fission will be cheap, but uranium will get scarce, so let's build fusion reactors that have cheap fuel!" Except fission didn't get cheap, the cost turned out to be dominated by the cost of the power plant, not the fuel, and fusion reactors don't solve that problem AT ALL.
