I would speculate that it's a combination of factors:
* Morning rather than middle of the night - possibly higher alert level due to the fact that it's not necessary to drag any high ranking officials out of their beds
* Very slow aircraft. Fighter jets caught up with it and the first order to land was issued when it was over 300 nm inside Indonesian airspace. At the cruise speed of Beechcraft Travel Air, that's something like 2 hours from appearance to intercept.
* Pepper and turpentine enemas which undoubtedly were administered liberally at all levels of command inside Indonesian Air Force when it turned out that they missed MH370.