There were a few posts and kickstarter comment updates where Larian explained why they went with Steam for the DVD version (fastest/easiest distribution method, would allow a day 1 patch to incorporate updates since the DVDs started production right up until release) and why they didn't consider it DRM (the game itself is DRM free). Those summaries are a little inaccurate, since they leave out details and nuance.
Availability to non-backers was a GOG issue, which they have since changed their mind about (and will release the game soon rather than wait for GOG Galaxy).
Larian wasn't trying to forcibly change anyone's keys to Steam. Most people wanted Steam keys. Rather than revoke all the keys as planned and re-issue the majority of keys as Steam, Larian decided it would be better to have the alpha/beta keys become the full version by default, and let people who wished revoke the keys to get GOG keys. Unfortunately, that meant the Vault website had to be updated to support that. I think Larian was hoping to get that done today, but it is getting a little late in Belgium...
Communication could have been handled better, but Larian was focused on finishing the game.
There is a limit on how many times, or how long, a game can be delayed.
