I also wanted to mention, I believe you and many others feel comfortable using it, because it has become EXTREMELY common among public speakers. The current (2023) White House Press Secretary, and the guests that join her, use it. We've also witnessed press releases from several police agencies using it. Professionals who become detached from proper grammar, risk appearing less educated, and infecting others around them with their misuse of words. Imagine if we started speaking or writing phrases like "We were at the grocery store today for so but food for the party".

Using the the coordinating conjunctions side-by-side, with one another, is off-putting, and portrays the writer, or speaker, appear less educated. Take these common coordinating conjunctions for instance: "For", "and", "nor", "but", "or", "yet", and "so". Using ANY of these, side-by-side, is akin to a "double conjunction". Not only is it not needed, but also sounds incorrect. In summary, it makes your piece, wordy.

You mentioned this is Formal Writing you're adding this sentence to, so I would use the in front of the word most. Worth mentioning however, non preferably, the word most is able to stand on its own in this sentence. In addition, I would omit the needless word "That", and replace it with the more appropriate comma after the word "Is". So it reads; "What fascinates me the most about the textile industry is, it drives the economy of many third world countries.". "The most" is also preferred as it is the superlative of the action verb "drives".