What changed
The emphasis moved to meditation, to the Buddha's own experience rather than the marvels around him, to compatibility with science, and to individual practice. Merit transfer, deities, relics, the rebirth cosmology and monastic authority were played down, not usually denied.
David McMahan describes this neither as a betrayal nor as a purification, but as a hybrid: something formed where Buddhist traditions met European Enlightenment thought, Romanticism and Protestant Christianity, and which then became a tradition in its own right.
1893 and after
At the World's Parliament of Religions in Chicago in 1893, Anagārika Dharmapāla and the Rinzai priest Sōyen Shaku presented Buddhism to American audiences as reasonable, ethical and universal, and were well received. D. T. Suzuki, who came to the United States soon after, continued in that vein for half a century and did more than anyone to shape how the West reads Zen.
Who made it
Not Westerners. Asian reformers were the main authors of this Buddhism, and they built it to defend their traditions under colonial rule, in a language the colonisers could not easily dismiss.
It is now the Buddhism most people outside Asia meet first, and it has travelled back into Asia too, so that a meditation centre in Bangkok and one in Berlin may teach in strikingly similar terms.
Why it matters
Much of how Buddhism is presented today, especially meditation-centred Buddhism, grows out of these movements.
History and tradition
What historians can say
Buddhist modernism is a family of movements, not a school with members. Erik Braun's study of Ledi Sayadaw shows that one of its most influential strands, mass lay insight meditation, grew out of conservative Abhidhamma scholarship inside Burmese monasticism rather than out of contact with the West.