Hindus often see Buddhism in a similar way that Catholics see Protestantism

 In other words it is an evolution or off shoot of the main religion being either Hinduism or Catholicism.

Guatama Buddha was a Brahman Prince of Lumbini which was a kingdom which is on the border of India and Nepal today. Then at a certain point he left the palace as a Prince and cut his long hair off and became an ascetic near Bodhgaya where he eventually became enlightened when he created the Lam Rim path which translated means "The Middle Way" path of Buddhism. It reminds me in many ways of the Greek saying: "Moderation in all things". It's a way to become enlightened without becoming an ascetic and fasting and doing self mortification all the time.

So, Buddhism is very popular and always has been because it is a moderate path not too extreme in any direction which also supports families and civilizations in this respect. It is based upon the ending of suffering by fostering compassion for oneself and all beings in the universe in the past, present and future.