part 2 explained that obito was training, then he saw rin die, then was end back to train some more then he in a way made sure the "pain" didnt die then he was pulling the strings for the akatsuki as well as caused the nine tails attack. he was with the akatsuki the whole time secretly but wasnt exactly relevant enough yet to bring into the plot line.
Akatsuki was probably attacking and Tracking down other Jinchuriki. If they were going to attack the 9T, they are probably trying to capture some others, Specifically the 7 and 5 tails, since the others are all accounted for, even if it's only in the anime.
Honestly he had to go into hiding after the Uchiha slaughter and in the grand scheme of things Part 1 was only a year or 2- not a long amount of time for Obito at all.