Yeah I think the main driver is neoliberal austerity doing what it does. The wing of the party in charge are basically Thatcherites. They want to the market to decide who gets access to basic necessities and bureaucracy to decide anything else.

In general I think neoliberals are becoming embarrassed by the fact that evidence based medicine is increasingly at odds with capitalistic ideals around how workforces should comply with the rich. So they want to introduce an apparently technocratic (which will inevitably be as low skilled tickbox bureaucratic as you like) body to replace actually qualified people - doctors- in this area.

I think it’s also a bit of a reaction to changes in the geopolitical scene. They’re hoping that in the event of further war in Europe that desperate but physically able people will be coerced into the military. By taking the ability to decide who is sick out of the hands of doctors and into the state they make this a lot easier. Similarly, more money for manpower and munitions by not paying out in benefits.