Complex sentence: The year 1964 saw Lenôtre enter the catering field which due in large part to improvements in freezing food perishables led to the broad expansion of the numbers of diners he was able to serve.
Split into simpler sentences: The year 1964 saw Lenôtre enter the catering field. Due in large part to improvements in freezing food perishables, he was able to quickly expand the numbers of diners he was able to serve.