@r10s was upset that there was no real alternative to WhatsApp, because of it’s network effect(nearly everyone has it, so you need to have it too)(https://en.wikipedia.org/wiki/Network_effect).
Then he had an idea - everybody has an email account these days - so why not chat over email?
Because he didn’t find a good app that offered chatting over email at the time, he started making one himself.
When there is so much interest we might do a (timeline?)page on the website about delta chats history…
Anyways until then you can find information in the blog https://delta.chat/en/blog
Also I’m not a press contact/person, so rather ask @hpk or @r10s…