Translation:They got married quickly because they were expecting.
https://www.collinsdictionary.com/dictionary/english/be-expecting if is it not applicable to a pair, you can reply.
"expecting a baby" is of course accepted
Perhaps you can elaborate on "indirect speech?" The specific issue I am having is connected to the sentence "stěžoval si, že polévka je studená" and this sentence. I am confused as to why we use present tense "je" in the quoted sentence and past tense "čekali" in the above sentence. They both appear to be talking about the state of something (soup, themselves) when they did something else (complained, got married).