I've approached it by reading and thinking about the company's relationship to it's stakeholders. Understanding and writing mini-essays on the current customers and their pain points, the main competitors and their products, the history of the industry/segment and more.
Information sources include YouTube, podcasts, press releases, news articles from niche sites, research paper summaries and various websites.
Networking of course plays a role, where I've sought out friendly people a few years ahead of me when it comes to industry knowledge. Mostly through existing contacts I'd do this again if I needed to, and would make sure to leverage each new contact to introduce me to further relevant people.
I've asked ChatGPT specifically to detail out how a MBB-consultant would approach the knowledge acquisition challenge, as they are adept at quickly navigating and learning a new field in a short amount of time. This has helped somewhat and suggested I'd sit down a perform a few different types of analyses.
As for rote learning, I've bought into the Anki flashcard system where i study acronyms, enemy materiel NATO designations, specifications and more.
To wrap up, I've studied finance myself and I have a strong feeling that there's a low correlation between financial-academic success and proficiency in marketing in the industry... Best of luck!