Tourmaline Labs Backend Developer interview questions

Had a phone interview, which was fun, then was brought onsite to do 4 hour long one-on-one interviews with various members of the company. Some interviews were technical others were higher level. Went out for lunch with them as well, all in all it was a really great process. I was not extended an offer and offered no explanation as to why. I politely asked via email and received no response. After spending almost a whole day at their office, it'd be nice to get at least a little explanation.