I sat through a great presentation at CERN the day the Higgs was discovered. The physicist who held the dissertation did an absolutely awful job. He honestly could not string together 10 words together into a single coherent sentence to save his life. He was "The guy in the barrel" that day. It was his job to speak to the visitors and explain what the purpose of the LHC was. He went through a stack of slides presenting the principles of particle physics and strangely enough even covered a little quantum physics which I found strange. He clearly hated speaking in front of "normal people" and beyond simply hating it seemed to lack the ability to do so. I've worked with similar scientists (as a translator to human) in other fields for years. It was basically my "turn in the barrel" because I would be responsible for saying "I think your brain is going far faster than your mouth and you skipped... I don't know... about 16 years worth of information in our terms because you didn't even remember where your mouth currently was. You need to take a step back... talk to me like I'm roughly as intelligent as a single cell organism and dumb it down a bit". I would then take what they said and run it though about 150 Google searches per minute of speech and then present "He said he wants pepperoni".
These guys are amazing and I'm not kidding when I say that the ones who smoke the bowl are far easier to communicate with. It slows them down to only 5 times human speed. On the other hand, given them nicotine and caffeine and their speed triples. They are well know for walking around with 5 or more nicotine patches and a 350ml cup of espresso and sugar when they're onto something. If you've see the movie "Hoodwinked"... think of Twitchy with a 190+ IQ.
That being said... scientists absolutely do postulate theories by plucking crazy ideas from their asses. Ideas like quantum pairs and dark matter almost certainly start off as wild assed guesses. And those are the absolute best theories out there. They take a certain level of creativity that is upon epic levels. BUT!!!! those are leaps that are founded on what is believed to be some sound principles.
Though there might be a ton of "If this is true and we believe this theory based on that is also true and therefore this would seem reasonable... it is possible that our lack of ability to observe this is likely because it's some form of matter which can't be observed since we only know how to observe matter as we already understand it. This other wild ass theory talks about anti-matter which we now seem to believe is actually quite possible, but now that we believe we can in fact observe anti-matter.. maybe there's some other state of matter we still haven't discovered that could be... counter-matter! Wait... counter-matter, while technically accurate sounds too much like anti-matter... we need a name for matter we can't really define yet and we also can't really observe... hmm... while simply being too black to see would be entirely wrong as simply not seeing past it would be good enough to detect it, this is more like invisible matter or truly transparent matter that neither absorbs, stores, etc... light or other EM we use to identify matter. Maybe we can call it vacuum matter... sounds stupid. So, for pop science we'll call it 'Dark Matter'... it worked for Superman. Though Bizarro was far cooler, but 'Bizarro matter' just is a little to DC comics."... then before publishing something, the progenitor (proper word?) stood up at a symposium an presented his theory (though it's more likely there was some correspondence before hand) and threw the idea out there with the some fairly vague theory that would apply some level of math or at least references to corresponding science to describe the properties of some sort of "dark matter" that would describe something that appears to have mass without actually being observable other than by consuming space where there should have simply been vacuum.
There was a hell of a leap of faith and to be fair, last I heard, the state of dark matter is currently still unable to be observed either in space or within a laboratory experiment. In fact, if I understand it well enough, what is really freaky is, we work under the presumption that what defines dark matter is something which contains a specific set of properties and more precisely is matter which clearly defines properties dark matter CANNOT contain and as such, if at some time we manage to properly observe what we assume is what we define as dark matter today and find it runs contrary, we'll have to use another name for it. The reason is, the properties of dark matter as a scientific and mathematical theory provide the foundation of many other theories and while dark matter may in fact not exist (not as in not exist, but not actually exist as dark matter itself would not exist as a principle in one way but would exist in the other context... if I understand it as it appears to be currently theorized) therefore other theories and sometimes principles would fail without the existence of such dark matter.
So why wouldn't we just alter the meaning of dark matter to refer to the actual "thingy ma-bobby" (scientific term if I understand it correctly) instead of renaming what we do actually observe even though it would cause all the other theories to implode? Easy... just because we figure out what that non-stuff is, by actually observing it, it doesn't mean that those other theories didn't manage to describe many other principles of science correctly. Often, those other theories will use something that is basically a flawed theory without depending on the founding theory to be actually correct.
Some people need the wild assed crazy idea of something like dark matter to exist and be real in order to establish the foundations of their own math and theories. And their theories still stand true with or without the existence of the thing they founded it on. Instead, dark matter will move from a theoretically real thing to a series of rules which define the conditions needed by something else. Just because dark matter turns out to not be real doesn't mean that the definition of those properties has to change.
BTW... now I have to go figure out if we still purely theorize dark matter or whether we've observed it and confirmed it or if we've observed and confirmed something else and simply kept the name dark matter to confuse the shit out of people using it's definition of properties by making the journalists happy.