Rejected for a job - would love to hear advice from a recruiter

I recently applied for a job, had the screening call with the recruiter, then interviewed with the hiring manager, and then made it to the final round of interviews. The role is in my field of learning and development, but training a technical team, which I have never done. I was very honest and upfront about not having created training programs for tech teams before, however, I work very closely with engineers and I am a fast learner. I did not once misrepresent my skills. Furthermore, from my conversation with the hiring manager, this did not seem to be a major issue, as her team consists of people with varying backgrounds; and one of the team members who interviewed me has a similar background to me. I then received a polite rejection stating that I don't have enough technical expertise for the role. That's fine, but why put me through interviews? I am genuinely curious as to why I wasn't just immediately rejected based on my lack of technical expertise.