LSAT authors typically bring up examples to support a broader claim they've just made. If a question is asking what something was "an example of", the test essentially wants you to paraphrase what broader claim the author was making in that paragraph before the specific example was mentioned.
In paragraph 2, starting around line 20, the author is explaining Modernism's dominance in architectural criticism.
If you weren't a Modernist, you tended to be dismissed.
If you were starting to get famous and you were maybe kinda Modernist, like Wright and Wagner were, critics would only focus on the Modernist aspects of your work.
So Wright and Wagner are examples of architects who weren't necessarily Modernist, but critics chose to fixate on those aspects of the architects' work.
A) "appreciated by the public" has nothing to do with why the author mentioned these architects.
B) this sounds a bit like what we were anticipating.
C) this is a misinterpretation of the text. The author was not saying that these 2 architects popularized Modernism; the author is saying that Modernism's popularity caused critics to focus on the Modernist aspects of these 2 architects' work.
D) How Wright and Wagner interfaced with their clients isn't mentioned at all.
E) Nothing in the passage specifies Wright and Wagner's "early work". The passage suggests that their work was somewhat Modernist, somewhat not and that critics chose to only focus on the Modernist aspects.
(B) is the answer. Admittedly, it is a bit of a stretch from what is given in the passage. We can't really point to any wording that says that Modernists "claimed Wright and Wagner as their own". However, the fact that the critics only spoke of the Modernist aspects of the work while ignoring non-Modernist aspects supports the idea that the critics wanted to represent Wright and Wagner as Modernist.