Knowing the space that you're working in when you're a contract recruiter is far less important than being a good salesperson.
I don't care how many technically aligned recruiters you've read articles from over the years, the simple fact of the matter is that the people who are at the top of the leaderboards at these companies couldn't give two shits about the technology. Their job is to land asses in seats, and they are ultimately in a vastly better position if they focus and refine their talents on selling and networking as opposed to learning about the problem domain. I still keep in touch with people from my recruiting days, and the high school dropout with 3 years experience when I joined a company is still a senior manager over the Cornell grad. They both make excellent money, but the dropout is easily the better salesperson.
When you've interviewed enough people, you can sniff out the bullshit artists, and virtually all decent to great candidates have a certain cadence to how they describe their roles and responsibilities regardless of the tech stack. I don't need to know the ins and outs of SAP AR and Treasury, I just need to know that the candidate has a consistent work history, is up to date, and can confidently describe their work. Client managers are more likely to go back to recruiters who can consistently put candidates in front of them, which is yet another reason why the numbers / networking game is more important.