Good Answer ! Just make a flow chart diagram as its a chronological question.
Also try to use Locus-Focus typology of N Henry / Discipline vs Professional changes etc.
Further you can talk about how initially pub adm varied as per changes in American Ecology mainly - but later post CPA its response ecology has turned global.
Also You can briefly DRAW about Indian Administration changes in last many decades !
Finally give it a current touch and tell how Pub Adm is expected to change POST-COVID19 emergency and how it rebrought focus from Market to Govt bureaucracy as a prime actor of governance !
Overall your answer is good. Just giving u some add on dimensions !! Best wishes. Keep writing !
After seeing this, I am sure I have to make plans for 2020 Mains!