Such insurances simply spread the risk of losses due to this kind of corruption among multiple entities. They don't provide incentives to the country to reduce the risk itself, which is the key differentiator.
And it does it with a far lower cost to sovereignty.
This misunderstands what incentives are at play for politicians with low accountability in developing countries. The cost of corruption is borne by these investors and domestic consumers, but the benefit of it is entirely concentrated in the political class. Therefore the opposite incentive exists, and the system becomes more resistant to any changes towards more inclusive institutions.
>sovereignty.
Meaningless buzzword. If a nation no longer favours the basket of benefits and obligations, it is entirely free to leave.