Do you think Sony, let alone Verizon would cave and agree to the terms of the GPL? Remember this is in 2008 - Sony's DRM/rootkit scandal was only 3 years prior (2005).
Edited: fixed my years
Also, just to clarify, the pill really isn't all too bitter. Use of OpenJDK wouldn't have dictated that all apps must be GPL -- not even bundled apps made by the manufacturer. The OpenJDK has a clear "classpath exception", which makes it more like LGPL -- any code dynamically linked with it is not required to be GPL. The only implication is that any modification they make to the actual runtime itself would have needed to be GPLed. I don't think phone manufacturers make any technologically groundbreaking, game-changing changes to the runtime -- anything that could hurt their competitiveness had it been free.
So I can understand Google's decision, and they certainly believed going GPL was an opportunity cost, but in retrospect, choosing OpenJDK would have -- at the very worst -- delayed Android's adoption by a single year, but would have ended making everyone's life much easier. I think that in hindsight, it's clear that passing on OpenJDK was a big mistake. Don't fear the GPL.
* March 2007 -- Sun open sources the JDK at the perfect moment for Google to adopt it. Google chooses not to because they don't like the GPL.
I think the phone vendors would have caved. It might have taken another year, but they would have realized they had no choice once the app store opened in July 2008, as none of them could have had the brand recognition to build an attractive software platform to rival the iPhone.