Pope St. John Paul II declared St. Isidore of Seville the patron saint of the Internet because he tried to catalogue everything that was ever known to man. I remember reading about this in 1997 in the Italian version of the L'Osservatore Romano.
In 1997 Pope John Paul II declared Isidore of Seville the patron saint of the internet. Saint Isidore died in the year 636, long before the first host-to-host ARPANET connection in 1969. But Isidore did try to record everything ever known in an encyclopedia that was ultimately published after his death.
From The Telegraph:
Saint Isidore wrote a 20 book opus Etymologies, also known as the Origins, in which he tried to record everything that was known. Published after his death in 636, it was for a thousand years considered the encyclopedia of all human knowledge.
Written in simple Latin, it was all a man needed in order to have access to everything he wanted to know about the world but never dared to ask, from the 28 types of common noun to the names of women’s outer garments.
It was a tool by those seeking wisdom much like the internet is used now.
Source: The patron saint of the internet is Isidore of Seville, who tried to record everything ever known
The Franciscan Media has this to say about this subject:
An amazingly learned man, he was sometimes called “The Schoolmaster of the Middle Ages” because the encyclopedia he wrote was used as a textbook for nine centuries. He required seminaries to be built in every diocese, wrote a Rule for religious orders, and founded schools that taught every branch of learning. Isidore wrote numerous books, including a dictionary, an encyclopedia, a history of Goths, and a history of the world—beginning with creation! He completed the Mozarabic liturgy, which is still in use in Toledo, Spain. For all these reasons, Isidore has been suggested as patron of the Internet. Several others—including Anthony of Padua—also have been suggested. - Saint Isidore of Seville
Popes generally do not name patron saints as the faithful often are inspired to have their own local patron saints. How Pope John Paul decided to have St. Isadore as the patron saint of the Internet is unknown. How he became (by what individuals) the patron saint of computer programmers is equally unknown. But it is a logical step after the internet patronage question was made.
In 1997, Pope John Paul II decided that the internet could use a patron saint to guide Catholics in its proper use. He chose Saint Isidore of Seville (560-636), Doctor of the Church, and last of the Latin Fathers. His twenty-book opus (called Etymologia, after the subject title of one of the books), made him an easy choice. The word “etymology” was Isidore’s own coinage. It means “the study of origins.” Today, the term is limited to the history, or origin, of words. Interestingly enough, three other words that I know of owe their invention to saints: “utopia” and “integrity” to Saint Thomas More and “soliloquy” to Saint Augustine.
Here is a prayer to Saint Isidore that should be said before logging in on the internet:
Almighty and eternal God, who created us in Thy image and bade us to seek after all that is good, true and beautiful, especially in the divine person of Thy only-begotten Son, our Lord Jesus Christ, grant we beseech Thee, that, through the intercession of Saint Isidore, bishop and doctor, during our journeys through the internet we will direct our hands and eyes only to that which is pleasing to Thee and treat with charity and patience all those souls whom we encounter. Through Christ our Lord. Amen.
Source: Patron Saint for the Internet, Isidore of Seville