Weaker systems are less likely to get pulled north into the weakness in the ridge which has developed due to Harvey...As I understand it, the stronger systems with vigorous circulations tend to slide to the right due to friction and drag factors and that certainly is lessened with a weak system.
TD 9's llc is clearly on the northern extreme of a pretty deep envelope of moist air to its south and east, and is in a dry pool that may beginning to give way to the moist air...
It is clear if the llc had stayed near its convection that it began to build yesterday the system would be deepening now.
I am curious though why that last remaing convection shows signs of shear...I can see nothing that would have blown the convection to the SW of the center or caused the LLC to jump NW as it did.