That article you cited said the defense wanted vehicular manslaughter and the prosecution wanted murder. In CA murder comes in various degrees, but I don’t know the statutory details of each, nor which degree the prosecution wanted.
The jury found for the defense. Which implies to me that the jury believed that whatever additional factors had to be present to find murder were inadequately proven by the prosecution. Or that the jury, a la nullification, chose to use some standard of comparative fault or comparative contribution to the fact the woman died, whether or not that is properly a part of the legal / statutory standard.
As always, we’ll never know what the individual jurors or the jury as a whole was thinking when they rendered their verdict.