First, patents carry a presumption that they are valid. The jurors were impressed with this presumption, and have a high level of confidence in what the patent office is doing.
As far as Microsoft’s claim that the i4i patent at issue should be invalidated, Greer [the jury foreperson] says she didn’t buy that argument: “I really felt like with experts in the patent office…they knew what they were doing. I suppose I really have a lot of confidence in the U.S. patent office.”
Second, the jurors felt that the case was important, and didn't think Microsoft treated it as such. They were particularly offended that none of Microsoft's higher executives participated in the trial.
A second juror, electrician Jarrett Stephenson, says he was struck that Microsoft’s lone witness was a software engineer, unlike i4i, whose founder, Michael Vulpe, testified. “I think a lot of the jurors, we all thought if this was that big a deal to Microsoft, they might have had some of their more executive-type people present."
I encourage you to read the full article.