Naruto Shikamaru was able to assist Kakashi and Naruto in both generations of Naruto? Personally, I think it is related to shikamaru's ability characteristics and the overall situation in Kiba Village at different times, which is explained in detail below.
The main reason why Shikamaru was able to become Kakashi's think tank was that the unexpected death of his father caused Shikamaru to adapt to the position of think tank in the management of Kiba Village in advance.
The Nara clan of Kiba Village are strategically oriented from there, and both Shikamaru and Shikaku have excellent big-picture views and IQ.
The fact that the Ninja Alliance gave the main staff function to Shikamaru's father during the Fourth Ninja War shows the extremely outstanding command skills of the Nara clan.
If nothing else, Kakashi's candidate to become Naruto's brainstorm should be Shikaku, both capable and prestigious, and Shikamaru is a little less talented than his father, but his life experience is a little worse.
Kishimoto forcibly let Shikaku receive a box lunch, and KibaMura was severely depleted after the Fourth Ninja War, especially the serious shortage of talents in command and strategy, and could only let Shikamaru assume the role of Naruto's think tank. After all, in terms of ability configuration, Shikamaru has unique conditions, and as for the lack of experience, he can use time to make up for it.
In fact, Shikamaru's performance in Naruto is still remarkable, and he has used his ability to turn the tide many times. The reason Kibamura chose Shikamaru to assist Kakashi was that he valued Shikamaru's ability and was the best choice made under objective conditions.
After Shikamaru had been practicing for a while, it just so happened that Naruto had the conditions to become a naruto, and the relatively harmonious relationship between the two sides allowed Naruto and Shikamaru to cooperate well in management.
If you observe the advisors and think tanks of the previous generations of Naruto, you will find a characteristic: most of the roles that can become naruto think tanks and advisors have a relatively close relationship with the generations of Naruto, we take the three generations of Naruto as an example, the consultant chosen by the ape flying sun chop is actually his former classmate (below), the ape flying sun chop belongs to the same class, know each other's situation, plus there is a sense of trust between each other who have performed tasks many times.
Including Tunzang was able to enter the core management of Kiba Village, which was a classmate of Ape Flying Sun Chop, and was also selected into the second generation of Naruto Guard Squad later, without these interpersonal blessings, Tuanzang's personality characteristics and the relatively mediocre ability of the two consultants mentioned earlier were basically unable to assist Ape Flying Sun Chop.
The relationship between Shikamaru and Naruto is actually very close, when he was a child, when most of the members of Kiba Village rejected Naruto, Shikamaru was one of the few who was willing to play with Naruto, so I personally believe that the trust between the two sides is actually far greater than many other Members of Kiba Village in Naruto.
Moreover, Shikamaru and Kakashi, Naruto have both had the experience of working together on missions, and Naruto and Kakashi have a better understanding of Shikamaru's ability characteristics and personality, so that Naruto continues to choose Shikamaru as a think tank to assist himself, that is, nepotism and meritocracy.
Shikamaru is a great fit to become a Naruto think tank, both in terms of relationships and personal abilities. Coupled with years of experience as a Kakashi think tank, Shikamaru's life experience is enough to take on the stage of Providing a series of decision-making suggestions from Naruto Oto. Moreover, in addition to Shikamaru, there are no other newcomers in the subsequent Kiba Village who are similar to Shikamaru's ability characteristics, in this case, Shikamaru can only choose to continue to serve as Naruto's think tank.
Finally, to sum up, I personally believe that the reason why Shikamaru was able to assist two generations of Naruto was that it was a matter of time and place and in line with the criteria for Kiba Village to select Naruto's auxiliary personnel.
First of all, in terms of ability, Shikamaru did not have to say, the reason for assisting Kakashi in the beginning was the early death of his father and the fact that Kibamura had no more suitable candidate than Shikamaru, and continuing to assist Naruto was also due to Shikamaru's relatively close interpersonal relationship with Naruto and the accumulation of personal ability and experience. Please forgive me for the place where the analysis is not in place, and if you have other ideas, please leave a message to discuss.