The arrest was likely the instigator, but at that point it had long been clear that Reiser4 wasn't going to be accepted in the kernel mainline, and Reiser3 had

The arrest was likely the instigator, but at that point it had long been clear that Reiser4 wasn't going to be accepted in the kernel mainline, and Reiser3 had gone off into an 'unsupported' limbo. The switch would have happened sooner or later.