* Empathy with the folks who's thinking was alien to me previously. I learned through doing their job. I could communicate with them and work in their context in a way that allows me much more leverage and ability to have impact with engineering.
* I learned the semantics and pragmatics of running a large organisation which gave me the lexicon and confidence to be taken seriously doing it (therefore more leverage) and taught me lots of small but important tactical lessons (e.g. how to manage difficult shareholders)
* How to communicate complex technical subjects to people who either don't/can't/won't understand them.
* A HUGE network
I went back because I missed it. I wanted to do consulting as a way of getting better at being an engineering leader, not leaving it forever. I was offered a few things at VC/PE firms, or in typical 'business' roles, but none of them really appealed. Not my passion.
I had never thought of the big 3 as possible route post-sale. Sale is not on the radar atm so back to my daily operational duties in my small yet thriving company :-)