Actually a few things over this debate overall
Bloodlines getting weaker:
It is something that can be considered when looking at the Rakatan Empire, it fell because the force grew weaker in the Rakatan, until eventually the Rakatan in the Kotor era had no force connetion to speak off left.
The destruction of Coruscant is possible too, afterall Sidious said it had happened before. So it could have happened between Kotor II and TPM. Of course there is no evidence of this. However one could assume it happened in this time. Why?
Well a few things, Bastila said the Republic had existed for 21.000 years or so when she was around. The hutts ruled before that and the Rakatan before that. The republic could have been reformed but nothing about it being conquered. And the most powerful since that time did in fact not conquer it.
Then you have the fact that history does seem to go down the drain in time. Now of course Coruscant could have some records of it being captured but it would be more likely if it fell since Kotor II and the records survived from that time on. Its more likely, not necessarily true but more likely IMO.