The Knights Were Not Created to be a Secret Organization
The Knights Templar were originally a very open organization with nonmembers being allowed to enter the Templar homes and the Templars were known to do good in the towns and cities that they inhabited. The restrictions and the traditions of the order were widely known by those who were interested and prior to the 14th century there were few rumors about secret initiations or dealings of the Templars.
That changed once the Templars came under attack by King Phillip IV. The members of the Order suddenly had to find ways to hide who they were in order to avoid arrest and torture. Many of them shaved their trademark beards though it was not enough to evade detection. While having a beard was not part of the rules of the order the trademark mantle was.
Once Pope Clement V dissolved the order in 1312 there were many rumors that the Templars found a way to exist out of the public eye. The papal orders required that much of the Templar holdings be turned over to another Christian order, the Knights Hospitaller. However, some Templar organizations changed their name to the Order of Christ. Some credited the Knights Templar as being too powerful to be shut out even by the Pope and the King, which is why rumors persisted as to their existence underground.
The rumors were helped by what happened at the execution of Grand Master De Molay in March 1314. As he was being burned at the stake he maintained his innocence and devotion to God. He loudly proclaimed “God knows how is wrong and has sinned. Soon a calamity will occur to those who have condemned us to death.” Pope Clement V died a month later and King Phillip IV died in a hunting accident before the year was out.