This is due to an evil plot by Goneril and Regan to overthrow their father and posses his power.
This is also because Goneril and Regan realise that Cordelia was Lear's favourite as he tells her in act 1, scene 1.
This was a silly thing for Lear to do as it gave a very strong feeling of rejection to Goneril and Regan and prompted them to begin to plot against him.
The sisters fear that Lear is losing his mind as his behaviour becomes erratic and inconsistent.
Lear asks each of his 3 daughter to tell him how much they love him in order to obtain a portion of his land
Cordelia finds herself banished after she refuses to pay her father fake, loving compliments.
Is this her fault? should she just have gone along with Lear's
game?
Mabye cordelia had it coming as she should have just played along with Lear and got a portion of land
Lear's oldest two daughters pay him stupidly fake compiiments, and both receive large amounts of
land.
Lear probably shouldn't have proposed the love game in the first place, as it sparked of a series of terrible events for him.