ASIC development on SHA256 has been going on since 2011, with about 4-5 process node updates and 2-3 generation updates in between nodes.

Development for other algos is no older than ~2 years, and these all probably started at the very cheap 90nm node, so its very easy to get a 6x gain going from 90-45nm.

Its a little harder for SHA256 to see huge gains going from 16nm to 10 or 7. Bitcoin ASICs have pretty much caught up with the latest node tech, so there wont be any more crazy gains in the future.