The question I have is that at some point X taxes are collected and the economy is growing at Y, then the policies change and now X-5 taxes are collected and the economy grows at Y. What was the function of the 5 under the first regime?
Not taxing the citizens now gives you more room to tax them in the future. Or looking at it another way, cutting those currently implemented taxes can act as a stimulus for the economy, although one with poor measurability compared to other types of stimulus.