Complex sentence: At the time of the Act's passing, it was considered necessary as an incentive for the private production of nuclear power--this was because investors were unwilling to accept the then-unquantified risks of nuclear energy without some limitation on their liability.
Split into simpler sentences: At the time of the Act's passing, it was considered necessary as an incentive for the private production of nuclear power. This was because investors were unwilling to accept the then-unknown risks of nuclear energy without limitations on their liability.