Quote Originally Posted by The Archangel
Because the seal is degenerating and that makes the red chakra inaccessible unless he lets the kyuubi take over.
Doesn't that mean Fourth was quite a n00b to use a sealing technique that not only claimed his own life but also can't keep the demon sealed for 20 years, let alone allow the host to use willingly the bijuu powers like the other jinchuuriki have been able to quite freely? Doesn't make the revered past leader of the village look too good, and certainly no genius.