The psychological relationship between King Lear and his two older daughters, Regan and Goneril, has always disturbed me. Lear encourages his daughters to compete publicly for his affection and correspondingly a proportionate portion of his kingdom. Refusing to participate, Cordelia is turned out. It's a no-win situation. How can anyone reasonably expect sincerity of feeling in such circumstances? Of course the older daughters are scheming and deceitful. They've been emotionally and politically manipulated, probably all their lives. They are the product of their environment. Cordelia is the extraordinary one for dissociating herself from her father's attempts at emotional manipulation.
What Lear wants to do is hand over the responsibility of power yet retain all the attendant trappings of glory. While the cruelty of Regan and Goneril in their subsequent dealings with their father cannot be excused, it must be noted that he was imposing a considerable burden on their resources by insisting on retaining his now redundant retinue.
For a fascinating and disturbing re-telling of the King Lear tale, in modern idiom and from the point of view of Goneril, or Ginny, I recommend Jane Smiley's A Thousand Acres. Also made into a movie (1997) starring Jason Robards, Michelle Pfeiffer, Jessica Lange and Jennifer Jason Leigh.