I find it interesting that the example sentence is 鰐蟹で漢字を猛勉強中です when a sentence came up like this earlier. I agreed with @Leebo 's post which was this, but now I’m second guessing.
How does 鰐蟹で漢字を猛勉強中です work as a sentence exactly since the を implies a direct object. I found an example on maggiesensei that is 今、日本語を勉強中の人は、このサイトに毎日、来て下さいね, so can adding 中 just allow 勉強 to act as a verb in this case kind of like a している ending? (sorry about spinning this thread into a question lol)