Delonte's head just isn't screwed on right, that's why they traded for Dooling instead of making Delonte an offer. This isn't the first weird thing that's transpired in his time in Dallas.
Danny and Doc know exactly what Delonte can offer on the court, but also know exactly what kinds of headaches he can cause as well - and frankly, I can't really blame them for walking away. West had his chance to establish himself here, to prove that he can fit in, to prove that he can keep himself under control, and he couldn't do it. Loved him when he was here, and really hope that someday, West gets the help that he needs - but at this point I can't say I'm sorry he's not in Boston.
EDIT: I mean, this is exactly in character with the self-control/impulsivity issues Delonte has shown in the past. A serious question - is he off his meds?