He got the yips mate simple as that. I've played and watched a fair bit of cricket and have seen it from time to time. His was a bad case of it. At the time he had a lot to play for, he had a good NZC contract and had a lot of close mates in that team. The ICL was a different story - they weren't getting paid and they were surrounded by corrupt people.
A lot of people are getting carried away here. It's easy to sit there and go "oh yeah I remember that time that player had a shocker - absolutely had to be match fixing if he's being accused now". Fact is you don't know and you're speculating with no evidence. I'll be waiting until there is evidence.