This isn't the right picture, because a lot of it is due to shift to new income tax regime. A more accurate number would be to look at say number of people in >10L bucket, which has increased by 4x over an 8 year period.
A lot of it is driven by improvement in compliance. Systems talk to each other, there are collections at source, cashless transactions are being recorded and monitored.
I strongly feel this 88L.number is in no way a reflection of the truth. If these people also come under Tax purview, that is how government can reduce dependence on the ones paying taxes currently.
Source: https://www.moneycontrol.com/news/opinion/surge-in-indias-taxpayer-base-mirrors-upward-mobility-11696101.html