I have a rich, 30+ year background in both hardware and software and I have been working with Bitcoin for many years. My first foray into Bitcoin development began when I built a BitcoinJ-based hardware wallet (for my own personal use only), back in the days before hardware wallets were available on the market.
Rudefox grew out of my desire to create a custody solution from the ground up and offer consulting services around it. I picked up Jimmy Song's excellent book, Programming Bitcoin. I thought it would be fun to implement the exercises in the book in Java, using TDD. As I progressed, I couldn't stop myself from bridging the gap between a simplistic, educational, proof-of-concept implementation and a fully-Bitcoin-Core-compliant implementation. For extra kicks, I read through some of the relevant cryptography RFC's and hand-rolled hashing and deterministic-K algorithms. I found myself more and more frequently referring to the Bitcoin Wiki, Bitcoin StackOverflow and then to the actual Bitcoin Core source code for edge-case behavior specification.