Complex sentence: Demand forecasts for the use of the Chunnel Tunnel, for example, turned out to be far too optimistic and thus revenues received through the operation of the tunnel were much less than expected during the first few years of operation.
Split into simpler sentences: Demand forecasts for the use of the Chunnel Tunnel, for example, turned out to be far too optimistic thus leading to a benefit shortfall. The result was that revenues received through the operation of the tunnel were much less than expected during the first few years of operation.