They do enjoy explosions for the sake of explosions. Any time a myth involves something blowing up, they have to make sure they blow something up, even if the myth is false.
But I think they do a reasonable job in most cases of outlining what the myth entails and trying to find ways to test the elements of the myth, and eventually the myth as a whole. They don’t always get it right, but they will readdress complaints.
As for why the original program creators chose special effects people, the creators of the show wanted people who could build things in a hurry. FX people are trained and experienced at building things quickly and reasonably cheaply (whatever the task will allow). The program creators went to Jamie, who they had worked with on a commercial before, and he brought in Adam to cohost because they wanted someone talkative and outgoing - which Jamie is not. But the two of them make a good team. The “build team” was originally just that - three assistant FX workers for behind the scenes build up to aid in getting things done. But the show figured out during the first season that there was too much for just Jamie and Adam to do with hosting, so they brought the “build team” in front of the cameras.
By the way, the program creators are NOT the Discovery Channel. It is an Australian TV production company. The show is funded and produced for the Australian show, then reedited (i.e. with a new American narrator) for the Discovery Channel.
Well, I take that back. I don’t know if Discovery Channel has a more direct funding role now. It’s been a couple years since the history was explained to me.
As far as the OP, go to the Discovery Channel website, there is a mythbusters web page. They have a discussion board, which is a frequent source of myths that the show investigates, including lots of commentary and complaints that spark revisits.
There are definitely scientists who could do a good job hosting. They could probably do a good job coming up with scientific tests. But the challenges for TV also include being able to quickly build any type of apparatus, equipment, or test rig required. That means skills in machining, welding, metalwork, woodwork, glasswork, etc. What is required for the job is technicians - shop personnel. The Mythbusters are that - crafts people. And they get technical expertise when the myths require more insight than a mechanically inclined layperson can provide.
The only problem I have is that later I can’t always remember the results of any particular test. I may remember the myth, but the result will be fuzzy. And that actually meshes with the results of some research that shows that is typical.