There is a lot that we will never know because the Caravan is too small to require voice and data recorders.
A lot of data should be recoverable from the memory chips of any GPS devices on board. I am highly suspicious of the newspaper reports of a "controller" causing a diversion - there is a lot of journalistic interpretation in that report.
Either way. a VFR flight should not have been in cloud, especially in an area prone to cumulogranitus.
The MSA is 15000 feet which is a challenge in an unpressurised aircraft so they were obviously too low.