He did, indeed, know the theatre inside and out, and the people of the theatre knew him. Once he knew which box President Lincoln would be in, it was fairly easy to plot his course. The President had supposedly refused extra body guards that evening. Whether that would have saved him or not will never be known. Boothe did not plan on breaking his ankle when he jumped from the theatre seats to the stage.
Though he made an immediate getaway, the broken ankle was ultimately his undoing as he simply could not travel without the aid of a doctor. The leg was patched up, but his trail was hot, and the time it took to take care of the break allowed the captors to get to him. He was mortally wounded in the fight with those that had followed and found him.