Broadly, I think I’m fairly optimistic about “increasing the power, wisdom, and maybe morality of good actors, particularly during times pivotal to humanity’s history.”
(Baseline: I’m bringing myself. I’m also bringing 100-300 pages of the best philosophy available in the 21st century, focused on grounding people in the best cross-cultural arguments for values/paradigms/worldviews I consider the most important).
How to achieve power: Before traveling back in time, learn old Chinese languages and a lot of history and ancient Chinese philosophy. Bring with me technological designs from the future, particularly things expected to provide decisive strategic advantages to even small states (eg, gunpowder, Ming-era giant repeating cross bows, etc. Might need some organizational theory/logistical advances stuff to help maintain the empire later, but possible Mohists are smart enough to figure this out on their own. Maybe some agricultural advances too). Find the local Mohists, teach them the relevant technologies and worldviews. Help them identify a state willing to listen to Mohists to prevent getting crushed, and slowly change the government from within while winning more and more wars.
Desired outcome: Broadly consequentialist one-world government, expanding outwards from Mohist China. Aware of all the classical arguments for utilitarianism, longtermism, existential risks, long reflection, etc.
Other possible pivotal points
Give power to leaders of whichever world religion we think is most conducive for longterm prosperity[...]
In general I suspect I might not be creative enough. I wouldn’t be surprised if there are many other pivotal points around, eg, the birth of Communism, Christianity, the Scientific Revolution, etc.
Since this question didn’t get a lot of response on EAF, here’s the answer I wrote on LessWrong that I’m moderately proud of: