1. lots of room for progress, i.e. the theoretical ceiling dwarfed the current capabilities
2. strong incentives to continue development, i.e. monetary or military success
3. no obviously better competitors/alternatives
4. social/cultural tolerance from the public
Literally hasn't happened. Even if you can find 1 or 2 examples, they are dwarfed by the hundreds of counter examples. But more than likely, you won't find any examples, or you'll just find something recent where progress is ongoing.
Useful technology with room to improve almost always improves, as people find ways to make it better and cheaper. AI costs have already fallen dramatically since LLMs first burst on the scene a few years back, yet demand is higher than ever, as consumers and businesses are willing to pay top dollar for smarter and better models.