I can only assume but to me it looks like it was this sentence that triggered the reaction of other posters:
I want to know what is the best I can do to become very great at electronics and an expert at it?
This was followed by
I want to know almost all there is to know about general higher level electronics, that is, using the readymade components to build circuits.
which didn't make it better. You are already aware that electronics is a
hard subject to study, comprehend and successfully apply. For this reason, your statements are red flags because they suggest that you're either falling victim to the Dunning–Kruger effect or you're arrogant enough to believe that you can achieve where so many others fail. Now, I'm not saying you are one of those but either way, your statements don't come off as being humble. Humbleness is generally seen as a virtue among those who are skilled, though. A lot of us have already dealt with people who can talk big but don't deliver, wasting time (and maybe money) in the process. Such people are never humble, making non-humble people immediately suspicious. Anecdotal evidence suggests to me that almost every skilled engineer has been burnt by such people or observed others being burnt. It could explain the reaction you've seen here.
As BradC already wrote, "true" experts become experts not because they can study well but because they have passion - an inner desire - to dig deeper and allow themselves to be completely consumed by a particular subject. They want the answer to all possible "why"s and aren't afraid to go down the rabbit hole where others shy away. They persist where others give up. They work on projects that other people label as already being "good enough". By doing this, they accumulate knowledge that's not easily found elsewhere and allows them to complete truly difficult tasks - they became experts.
At the same time, "expert" is not a static term. If you go to a trade/industry fair like the Embedded World in Germany, you'll find a whole range of expert-level engineers and FAEs. They may only be an expert in one particular chip/software/architecture/domain/whatever but they're experts nonetheless, simply because their job is demanding and requires a person to obtain such vast amounts of knowledge. A layman would call them experts but to people of the trade, they may merely appear as skilled engineers. It's all relative.
If you had written that you want to become an expert in IC design, or an expert in system design, or an expert in circuit design then you would've defined a scope that's actually doable by a person who is both skilled and determined. As your post suggests that you want to become an expert in everything, the red flag comes into play.
I think I'd like to be an academic and work inside a university, and teach, however I don't enjoy teaching, I would enjoy the research side.
I can only speak for myself here, but this is also a red flag to some extent. By definition, universities exist for teaching
and research. Here in Germany, the outcome of this combined with never-ending budget cuts is that a ton of people who want to do research are forced to do seminars, lectures and labs as well. The result of this is that the education suffers as those people are neither passionate about teaching nor skilled to do it properly. In other words: they shouldn't be allowed to teach and people who
want to learn but are hindered by unskilled staff are left with a sore spot for this issue. You indicating that you wish to become exactly this kind of person could again trigger a negative response, even if it's not how you meant it.
My recommendation for you? Buy "The Art of Electronics" and see which chapters interest you the most. Not all possible fields are covered by the book of course but if you discover that one particular field is interesting you more than others then you could strive to become an expert in it. This may also happen during your university studies, of course. How to become an expert? Find something that motivates you (e.g. set yourself a goal by defining a project), learn of ways how it can be accomplished, study the underlying principles and methodologies, obtain and learn the tools commonly used for such work - and
do. Without doing, no one can ever make mistakes and learn from them. Without learning from mistakes, no one can become effective at solving problems and thus can't become an expert. Because experts are solving problems, hopefully ones worth of their time