Famous theories that popular culture and the internet (which is largely the same thing I suspect) think are proven.

The Big Bang. This theory postulates that the universe began in a very dense and hot state, when for reasons not understood it exploded outward. All the matter and antimatter hurling through the Void. Sort of like the All Father's Arc of Time theory . . . wait that last part is in the world of Aihrde. But regardless it is a theory. Places the universe at about 14 billion years old, which just seems . . . odd. the Big Bang explains lots of observable phenomena, but still has not been proven.

KT Extinction. This is the theory that the dinosaurs were wiped out by an asteroid striking the earth, causing either a global-killing fire storm (what Gary Gygax called the Rain of Colorless Fire) or since the theories of global warming have become dominate in modern discussions that the impact caused some type of atmospheric change. I never could figure out why the birds and the tiny mammals survived this event.

At any rate when you read articles that begin with "during the big bang" or "the KT extinction event caused" never forget they are theories only.

Much like TLG's production schedule. In theory . . . .


Please keep in mind that there are two primary definitions of "theory,", scientific and colloquial. The common, colloquial definition of the word is analogous to "guess" or even "educated guess," and this seems to be the way you're applying "theory".
By the way, the title "theorems" is a different word, which is used in mathematics; and theorems can be proven or disproven. A theory, however, cannot be "proven" in the absolute sense of that word.
The other definition of "theory" refers to the scientific usage, in which theory describes the best explanation or description of a process supported by overarching sets of facts and data. This is where we get theTheory of Gravity, Germ Theory, The Theory of Evolution, Particle Theory, and The Big Bang Theory. I would leave out the KT extinction as a proper scientific theory, since there are still competing hypotheses about what actually occurred.
Keep in mind that dinosaur extinction is but one of many extinction events on our planet - none of which ever resulted in the total elimination of life on this planet. These events each had different, and probably multiple catalysts, and played out over hundreds of thousands of years, generally. Climate change on a nearly global scale was a major driver in most instances, affecting the simplest, most basic lifeforms - prokaryotes, algae, etc. - creating a cascade effect as flora, fauna, and then megafauna die off due to disappearing food sources.
In fact, there were several moments where humankind nearly went extinct, leaving only bottlenecks whose genetic traces are visible in our DNA today.