In other words, he is good at impressing people who don't understand the topic; but the people who understand the topic remain completely unimpressed.

The first part without the second one could mean "great communicator". The first part with the second one sounds more like "crackpot".

It is easy to impress people when you have studied something longer than them. There are interesting ideas that are relatively simple to learn, so if you learn them and then explain them simply to other people, they are amazed.

But it is possible to get some beginners' stuff right, and then get some advanced stuff wrong. And the laypeople who listen to you are impressed by the former, and cannot notice the flaws in the latter. Then you claim to have found answers to some expert-level questions, and your fans go like "this is pure genius, why doesn't academia build statues in his honor?"

From my perspective, the part that impresses people is Wolfram pointing at a Turing-complete system (it used to be cellular automata, recently it is some graph transformations) and explaining what Turing-complete means. Which is fantastic if you never heard about Turing-complete systems before! Yes, in theory it could be used to simulate a universe, despite being such a simple thing. If this is news for you, it will completely blow your mind!

On the other hand, if you studied computer science, you know that Turing-complete systems are a dime a dozen. For example, almost any programming language is Turing-complete. Yes, it is fascinating to find things that are way simpler than the usual programming language, and are still Turing-complete. But again, if you studied computer science, you already heard about a few of them, so learning that there is yet another one doesn't sound so revolutionary. At best, you may admire its elegance, but it's still only one specimen amongst many.

So when Wolfram continues to explain how his currently favorite system could simulate the universe, you start yawning, because "being able in principle to simulate the universe as we know it" is a general property of Turing-complete systems. Yes, it is a property of Wolfram's current favorite system, but it is also a property of zillion other Turing-complete systems. There is no reason to single out this one specifically. You might as well talk about how the universe could in theory be simulated in PHP. Yes, it could, but without further evidence there is no reason to assume it really is.

(In fact, it's even worse. If something is Turing-complete, not only it could simulate our universe, but also any other universe with completely different laws of physics. Therefore, despite the fact that our universe could be simulated in PHP, you can't really hope to discover anything relevant about our universe by studying PHP. A universe without gravity, or a universe where gravity is a repulsive force, could be simulated in PHP, too. This is why you cannot find useful information about gravity by studying what can be done in PHP.)

...so far, this was inside my field of expertise, which is computer science; now I am going to step outside of it and comment on physics...

If I understand it correctly (and reading comments by people who know physics better than me suggest that I am roughly on the right track), the next step is Wolfram finding some vague analogies between some properties of his currently favorite Turing-complete systems, and the laws of physics as we know them. Like, if something grows, that is kinda like the expansion of universe; but if something shrinks, that is kinda like the relativistic contraction; and if two things are somehow connected to each other, that is kinda like the quantum entanglement. Maybe the actual analogies found by Wolfram are less lame than this, but ultimately they are just analogies, and probably sound equally lame to an expert in physics. Things kinda grow, but not in a way that would allow you to actually derive the equation for Lorentz contraction. They just grow, and that's it. If we wouldn't have the theory of relativity by now, you couldn't use this to invent it. It has no predictive power. First you must know the laws of physics, and only then you can search for something that is vaguely analogical to them.

And it is this combined effect of "finding a simple system that is Turing-complete" and "finding some analogies between the system and the laws of physics" that creates the strong impression in laymen that Wolfram found something relevant to understanding our universe. "Hey, if it can be used to simulate the universe, and if we can find analogies with some laws of physics, why don't we just study it further and maybe we will find some new, hitherto unknown, laws of physics? Why is the academia not paying more attention?" The main problem is that the fact that it could simulate the universe actually means much less than how it sounds, and the analogies can only be found when you know what you are looking for, in other words only after the relevant laws of physics have been already discovered.

EDIT:

Looking at this discussion, you can find people who defend Wolfram because he sounds exciting, or because it feels unfair that his theories do not get the attention they supposedly deserve. Not a single person is defending him because he explained some law of physics correctly. And this is not an accident. As far as I know, the same thing happens outside Hacker News, too.