I found this was the same for me in the middle of the pandemic hiring boom too. I sent off a dozen resumes and didn’t hear back from any of them, one post for me on the YC alumni forum and I had a whole week of interviews lined up immediately and one referral to another company which landed me an interview as well and ultimately an offer I ended up accepting.

I never found cold applying to be particularly useful, even during the best hiring times, so I always read these accounts of how bad the market is because someone sent their resume to X number of companies to be a bit useless in judging the market as in my experience that never really worked.