Complex sentence: During all this time, the only people who knew that Holmes was alive were Moriarty's henchmen and Holmes's brother Mycroft and the only reason for that was because Sherlock needed some money so he could travel and to keep his rooms just like he left them.
Split into simpler sentences: During all this time, the only people who knew that Holmes was alive were Moriarty's henchmen and Holmes's brother Mycroft. The only reason for that was because Sherlock needed some money so he could travel and to keep his rooms just like he left them.