especially since fillon is FAAAAAAAR more right-wing on economical issues and also dragged LR to the right.
He and his (adopted) wing of the party (Manif Pour Tous, hard conservative types) have a lot of convergence with Marion Maréchal-Le Pen and her wing of the FN though.
http://www.lefigaro.fr/politique/le-scan/citations/2016/03/15/25002-20160315ARTFIG00166-ces-elus-lr-que-marion-marechal-le-pen-imagine-dans-un-gouvernement-fn.php
(yes, I know sorry for the source)
A lot of commentators have actually noted how Marine Le Pen's neither Left neither Right campaign backfired when Fillon was elected, because her only way to power was trying to entice the hard right of the LR into governing with her, while the 3 given candidates (Valls, Macron, Juppé) were presented as the centre-left.
Personally, I just think it has to do with her father's legacy. And her niece can try a different strategy, unless they drop the idea that it is a Le Pen enterprise a can't see tribal UMP/LR voters take them seriously as the "Gaullists" Fillipot has branded them as. Especially voters old enough to remember the OAS.
Is Marine likely to step aside in favor of her niece anytime soon though? I wasn't aware that was a possibility in the near future.