The phrase "new imperative" refers to a newly important or necessary action or responsibility that is crucial for a certain situation or goal. Full definition
Firstly, it could be about Thanos» new imperative of preserving the integrity of this universe he's just reshaped and «perfected,» while for the heroes, their imperative would be to find the Mad Titan and undo the state of disarray he left behind. (cbr.com)
If you want suggested reading on this, look at the investing books of John C. Bogle who studied some of this rather extensively, in addition to being one of the first to create an index fund that became known as «Bogle's Folly,» where a couple of key ones would be «Common Sense on Mutual Funds: New Imperatives for the Intelligent Investor» and «Bogle on Mutual Funds: New Perspectives for the Intelligent Investor.» (money.stackexchange.com)
Robert N. Bellah, «Discerning Old and New Imperatives in Theological Education,» Theological Education 19 (Autumn 1982): 7 - 29. (religion-online.org)