Because they were invited to join.
Just like people go around talent spotting … masons go around looking for people who have an emotional and devotional effect on people. If you can steer the trend setters of society then you can steer society.
Yes, they were influential beforehand but after joining they were given a podium/platform to be even moreso.
The answer to the first question is answered by John Taylor Gatto … he says the framework of the Hindu class system was used and adopted for education, in basic terms ‘knowledge is power’ so you distribute your power according to the pyramid model and hence the majority of school children will learn about the successes of particular people ‘who were masons’, but not be told that they were ‘masons’.
Elites however are likely to get that information and more.