they do a single Google search, fail to understand the answer because typically they have the intelligence of a lump of cheese, and form a totally incoherent theory as a result

I mean, it’s more complicated than that on two levels.

Firstly, sports drinks like Gatorade were formulated for a very specific kind of short term high intensity activity (specifically, playing football in Florida during the summer). But for lower intensity and longer term exercising (anything over two hours - long distance running / biking / swimming, most notably) its generally worse for you than water. So expressing a degree of skepticism is warranted. That’s doubly so in the face of endless marketing and native advertisement in sports media.

Secondly, when you get into the dietary sciences and start running into contradictions between the more well-established benefits of drinking water relative to the dubious claims of marketing agencies, it can easily become difficult to determine what is and is not bullshit. Because Google itself has been marketed as a valuable tool for research and analysis, and because so much of our academic infrastructure has been privatized (Google being a prime example), even the most intellectually curious and level headed can become overwhelmed with the task of “Doing Your Own Research”.

Flat earthers primary reason for believing the earth is flat is that otherwise water wouldn’t form puddles and lakes it would always be flowing downhill.

The primary reason for believing the Earth is flat is that the ground is flat in much of the country. People don’t natively intuit that the earth is round, they have to be told or to engage in some fairly non-intuitive experimentation. To grapple with the idea of a round earth, you have to start taking second and third hand accounts at face value or get reasonably good at geometry and have a certain bedrock faith in the accuracy of your calculations.

I’d argue that flat earthers are more curious and often more intelligent than their “I believe the earth is round cause that’s what they told me” set. And its often this curiosity - combined with some error in logic or bad initial data - that leads them to try and prove the unproveable so doggedly.

But so many people fall into the trap of believing intelligence leads to correctness. You can be very smart and still end up with a very wrong answer. What’s more, if you’re surrounded by people you don’t trust (because you believe you are smarter than them), it can be difficult to convince you of your own failings precisely because you don’t have enough of an intellectual peer base to understand your reasoning, spot the mistake, and demonstrate a counter-example.