"My little brother loves anime."
It's split up to allow people the chance to practice "spelling" the word, not because they think it's 3 parts.
They have a habit of splitting words up, personally I find it annoying as hell. I don't know why they don't give the option for us to type the answer through our phones keypads, would be so much easier, and better for spelling practice for people.
Coupd always offer both options for inputting the answer like Memrise do. That way people who want to type can, and people who don't have a Japanese keyboard installed can still select them.
The app lets me use my own phone's keyboard. Coming up with the sentence without any choices takes the exercise to a new level of difficulty. Plus you can practice kanji or use voice entry (if your phone has the voice support for Japanese downloaded) for speaking practice
It doesn't matter why they did it, in an exercise like this where you're putting elements of a sentence in order, having a word split into three parts is awkward.
In the English sentence "my brother" is the subject of the verb "loves", but not in the Japanese sentence. This is because "daisuki" is not actually a verb like "to love" is in English. It is an adjective/noun meaning "loved/a love". So if we translate literally, おとうとはアニメが大好きです is closer to "As for my brother, anime is loved/a love", making "anime" the subject of the sentence (and "my brother" the topic).
は indicates the main, or new, subject. が indicates secondary ones, or non subject/non object nouns.
は also works as a comparative particle, eg; the speaker, unspecified subject of a previous sentence, and/or listener don't like what the speaker's younger brother does.
My word bank has not been offering critical word choices (such as アニメ or 大好き for this question), so I've resorted to using the keyboard option instead. I got the following correct, for FYI purposes: 私のおとうとはアニメが大好きです
Just curious, but should not adding です and ます really be incorrect? I understand it's to be more polite but i like to leave it out just to have it in its simplest form.