Source needed. I've been working in tech for 15+ years, alongside highly charismatic and competent people, terrible engineers with less charisma than my coffee pot, and everything in between.
You do not need to be charismatic to be a good engineer, but also it certainly doesn't hurt, and friendly teammates make for a better team atmosphere. If I'm considering two candidates otherwise similar, I'm going to go with the one that's more pleasant to work with.
Someone in the top 10% of competency or charisma will have average distribution of the other. If you consider the full population, you'll find no relationship, but because you are only look at the top 10% of each, those in the top 10% of one will be average in the other and vice versa. While some (~10% of each top 10% group) will be represented in the other group, you'll still find that they are more likely to be at the bottom of the group in the second group.
The end result is that if you only plot the data for the top 10% of each group, there will be an inverse correlation.
This can hold true even if there is a positive relationship between the two characteristics depending upon the strength of the relationship and how selective you are in selecting the top of each group.
This leads to some interesting results, such as when fruits are grown for look and shelf life risk losing taste and flavor despite these factors being unrelated.
Would you disagree that software development, as a profession, tends to have fewer charismatic people in it than other fields in which charisma is more valuable and/or essential? For instance, if I were to suggest that the average successful politician is more charismatic than the average successful software engineer, would you disagree with that statement?
If we think about it in purely economic terms, I'd suggest that people who are very good at getting other people to do things (i.e. they have charisma) have a powerful incentive to enter careers where they can leverage that special ability.
>Source needed
Experience and observation. When one is deeply involved in solving hard problems, one has less time for pleasantries, superfluous stuff ( but important to people in general) and subtle manipulations of relationships, that make up 'charisma'. Over time that becomes your personality. Not saying that this is the best thing to happen to an engineer, but it's the way things are IMO.
As someone who has interviewed many software developers, I can assure you that charisma is not something that experienced hiring managers in tech are expecting in the candidate pool. For sales positions, sure. For coding, though, competence is often inversely correlated with charisma.
Reasoning through technical problems is a different story.
I think your first observation about grinding leetcode is interesting. I suspect that this is the approach people take when they're trying to get picked up by big companies (FAANG or whatever). Programming problems become a quick way of winnowing the field for companies that have a highly process-oriented approach to hiring. My own experience has been in small companies, where being able to get in the door and make progress through the interview process is often dependent on one's personal connections/network, creativity and so on.
So my advice to the OP would be to leverage your network and try to get inside companies connected to people you know. Maybe look at smaller companies that aren't necessarily tech companies, but have a strong need for tech?