It's useful to think of the traditional relationship that Europe held with "the East" (broadly here referring to Islamic, Indian, and East Asian civilization). Average consumption per capita in Western Europe didn't overtake China and India until 1815 (see Kenneth Pomeranz, "The Great Divergence"). "The East" had always been a source of spices, sugar, and silk: it was associated with great wealth. It was a desire to tap into those markets that largely drove the age of discover (though I think the book is awful as a cohesive argument, David Landes does have a good overview of the age of Discovery and its motivations in "The Wealth and Poverty of Nations").

This economic exchange was accompanied by an exchange of ideas. Early Jesuit priests like Matteo Ricci began the work of translating Chinese classics into Latin in the late fifteenth and early sixteenth centuries (See Jonathan Spence's account of Ricci and his life's work), and this interest in the religions and philosophies of the east grew, with the first translations of sanskrit texts occurring in the mid to late eighteenth century.

This growth in exchange of goods and ideas was coupled with the rise of the "New Philosophy" (science) in the seventeenth century, and then with the Enlightenment in the mid and late eighteenth century. The enlightenment, especially, led to an increased questioning of traditional Western religious and philosophical ideas, with many Enlightenment thinkers becoming the first generation to reject the ideas of Christianity.

I would argue that the intellectual changes in the enlightenment period along with the growth the exchange between East and West in the sixteenth, seventeenth, and eighteenth centuries laid the foundation for the attraction towards oriental cultures in nineteenth century romanticism that you describe. David McMahans's "The Making of Buddhist Modernism" contains a detailed account of the interaction between Romanticism and Buddhism, but thinkers like Emerson and Thoreau were also heavily influenced by Indian philosophy. It was in the nineteenth century that the industrial revolution began to truly and fundamentally change the relationship between people and the material world. Vast urbanization coupled with unprecedented pollution led many thinkers to question the direction of Western civilization. This is reflected most clearly in the poems of Wordsworth, whose biting critiques of civilization and praise of nature are textbook examples of Romantic thought. Questioning the direction of Western civilization naturally led many to the "ancient wisdom" of "the East."

I'm not sure to what extent "commoners" participated in the rise of Orientalism, but I would first ask who "commoners" were. Emerson lectured widely and published many essays, and he was deeply influenced by the Baghavad Gita--if "commoners" adopted his ideas, were they "participating"? I would assume that it was a smaller group of people that were actually reading Eastern texts and applying them to the problems of Western society, but that doesn't mean that the influence was relegated to one subsect of society.

I'm not quite sure how to answer the last question--in your view, how is adopting foreign elements looked at today?