What could be the real reason why Abrams and Kasdan took over writing for SW episode VII?

My opinion is that Lucas ruined his own franchise by writing and directing the SW prequels. Feel a bit jittery Disney might mess up this upcoming episode too. Was confident Arndt, the writer of Hunger Games and who won an Oscar for Little Miss Sunshine, will deliver the goods but now, this news that JJAbrams and Lawrence Kasdan ( Empire Strikes Back writer ) are taking over the script.

http://www.deadline.com/2013/10/j-j-abrams-lawrence-kasdan-take-over-as-star-wars-scribes/