If you say that something is not so much one thing as something else, you mean it is more the second thing (Cambridge dictionary). 'Not so much as' is a set expression in this case. It is possible to rephrase this sentence like this: English culture was revitalized by contemporary Europeans under the influence of the classics more than by the classics directly. I guess "but" would be OK in this sentence too, although I would probably write "but more so" to continue the comparison that "not so much" started. English culture was revitalized not so much directly by the classics but more so by contemporary Europeans under the influence of the classics. Hope this helps ))

not so much as 是一个固定句式哦亲。

Felix, Both Yanyan and Halyna are right. I'd just add that it's a very odd sentence. It's not so much that it's stupid as it is that it's pointless. Obviously books take effect through the people who read them. Duh. Grammarly, the popular grammar app, wants a comma after the "obviously" in the sentence above. The New Yorker has a cartoon this week in which the lawyer is counselling the poor distressed client, "No, the refusal to use the Oxford comma is not grounds for divorce." I don't use their furshlugginer comma because I consider the "obviously" to be the point of the sentence, not a throw-away introduction. It's not so much that books take effect through being read as it is that this is so obvious as not to be worth saying.

"much directly by the classics" is an adverbial phrase and so can go into the construction "not as ....as". I like this version: "English culture was revitalized by the classics, not directly but through contemporary Europeans influenced by them."