It was not long after the 1930s commenced that such baritone singers as Bing Crosby and Russ Columbo contributed to the popularization of a type of romantic, soothing singing that came to be called “crooning.”

It was not long after the 1930s commenced that such baritone singers as Bing Crosby and Russ Columbo contributed to

Not long after the commencement of the decade of the 1930s, baritone singers such as Bing Crosby and also Russ Columbo decided to contribute in

Not long after the 1930s commenced, baritone singers like Bing Crosby and Russ Columbo contributed to

Not long after the beginning of the 1930s commencement, baritone singers like Bing Crosby and Russ Columbo had contributed to

It was not long after the 1930s commenced that baritone singers such as Bing Crosby and Russ Columbo had contributed in.

OA is A

i realize about the rest of the answer but please shed some light on the use of it and also 1930s commenced and also about- that such baritone singers as- what is the function of such in this sentence because it started after that +such

It's a tricky problem. A, while correct, is not ideal. But we get there by process of elimination.

We can begin a sentence with a general "It is..." or "It was...," but we need to follow up with "that..." Basically, the whole clause starting with "that" is the antecedent for the pronoun "it." The "such" is just part of the phrase "such as." In this case, that phrase is broken up to say "such baritone singers as" -- this is ok.

#50 in the SC section of OG11 has a similar problem that you may want to reference.