I don't deny that but look at Man U and Arsenal... They were champions and their managers were way more experience than Houlier in terms of winning championship.... They seems to be struggling right now...
Wenger is a very experience manager way better than houlier and when he decides to let Patrick go, i would think he has some solutions up his sleeves but look at where they are now... Even Henry is being linked with Barcelona...
Definitely it will be easier for any manager to take over a championship club and be successful but it doesn't gurantee so... Other clubs would try improve by buying better players.... So for Lyon to be leading by a big margin even after they sold Essien, i think to a certain extent, Houlier is doing a fantastic job.
Besides, Lyon is also doing very well in the Champions League...