I'd like to think that the US government changed the what it's measured because of changes to how the economy works (this is especially important for GDP calculations) and improved understanding of inflation. Doesn't mean that's the case, but I don't buy that because a metric is what we used in the past it's inherently better.
The changes increased government revenue by pushing people into higher tax brackets and decreased government spending by reducing COLA adjustments on social security and government pensions. It's politically a lot easier to obfuscate inflation than explicitly raise taxes and/or cut spending.
