Mao is a long story. I will skip this time.
Common sense means you don't really understand how to get a country, you jump into how run a well established country.
Country is not natural thing, it must be built base on consensus. Most undeveloped countries have not enough consensus at all. When you distribute the power by implementation of your secret ingredients: rule of law, transparency international, and independent institutions. You already failed in the first place. The ruler must grab as much power as possible to build up the country consensus, which means kill your political enemies or at least make them irrelevant politically.
Any successful ruler knew this, that's why they rule. Such as Bismarck, Stalin, Mao.
Why I say grown up in west lack of common sense, because you guys are too realistic. The west has deliberately ignore how they build their country from scratch and de-emphasize how many enemies they killed to get the country. The history is very cruel in most cases.
India leader, Gandhi has no clue how to build a country, nor Nehru. They are installed by British, that's why Gandhi was not assassinated by British in the first place. That's the fundamental reason why China and India are so different.
I answered your first question partially. Mao finished his task in his era, Deng did his respectively. Xi is doing his job. Different era, different task. It's a continued process for China renaissance.
India's future is dark because of the DNA of the country.