We didn't have 2nd degree murder when they charged him. They downgraded the cruelty charge. Both were felonies, but less burden to prove 2nd. Same felony murder applied to either cruelty charge.
Now though...
You're right. I spoke loosely. I should have said, always easier to get the non-intent crime proven. That said, the new law was enacted in April, so I have to think they were acutely aware of their retroactivity issues when they downgraded. jmo