As far as Vivek's interest in Monta is concerned, I'm not sure. But if I'm allowed to go out on a limb, I think it may be related to the manner in which Joe Lacob was booed at Chris Mullin's jersey retirement ceremony. If you recall, the Warrior fans wanted Monta traded so they could have a bigger backcourt. Trading Monta would allow Klay Thompson to start so they not only traded Monta but brought in one of the better centers that the W's have ever had in Andrew Bogut.
The rest was confusing though. For whatever reason, the fans booed Lacob out of respect for the outgoing Ellis. Supposedly, they thought highly of his work ethic and what he meant to the team. Being that Vivek was still a part of the Warriors ownership group, he most likely took notice of how popular Ellis was and as a result, sees a chance to add a "popular" player here.
There's also the thought that he can steal away some Nocal fans who were Ellis supporters. But that's just a long shot guess on my part.
As far as his free agency is concerned, I'm surprised that he and Fegan haven't looked at Philadelphia. They're at least $15 million under the cap and have no other SG on the roster other than an aging Jason Richardson who most likely won't be ready for the start of camp. If nothing else, Monta helps you if you're in tank mode since according to this thread, he hurts the team. Plus, they need to get to the minimum cap level at some point and with all the free agents having signed already, Monta is the last one out there who can get you to the $52 million payroll level.