I was relieved to find out that they were smart enough to use TS, yet horrified when I looked at the code base and found that the entire codebase was littered with the "any" keyword, making typing damn near useless.

We had so many bugs reports that essentially boiled down to "this data is being transformed in a way it shouldn't be". Almost invariably these bugs were due to the developer thinking that some variable represented one thing, when it really represented something else, and they thus performed an incorrect transformation on it. Typing would've eliminated this entire class of bugs.

Figuring out what any variable represented often involved traversing the huge codebase to find out where the variable originated. On some occasions, I even had to talk to the back-end developers to figure out what the heck was going on. Typing is self-documenting, and would've completely eliminated the need to go on a scavenger hunt to figure out what a variable meant.

Anyways I got sick of this rather quickly, and made sure to add types to any new code that I wrote. I was the only developer on the 20 person team that bothered to do so.

As an intern, I didn't understand why these developers refused to use types. I just assumed that with their years of experience, they must've had a good reason. Now looking back at it, it's clear that they didn't understand types, didn't want to learn how to use types, and thus just chose to completely ignore typing.

As you said, this is utterly horrifying (especially for a financial services company dealing with real money).