Found this trolling DataLounge
https://www.datalounge.com/thread/13474114-megan-hilty
I shouldn't really say too much, but it's anonymous here, so what the hell: Spielberg did not like overt theatricality and he did not like Megan. Every note he gave was about how her part should be recast. His notes were often personal and not constructive, and he rallied other producers to join this bandwagon. Other members of the creative team stepped in to defend her and her job, and were punished for doing so: Theresa Rebeck's first fight with producers was over Megan, which set the tone for the first season and her departure, and Marc and Scott were "punished" for defending Megan by having their contributions eventually reduced to just Megan's storylines, which they were not unhappy about...
As feedback rolled in during the first year, and it was mostly negative, Spielberg became convinced that his fixation on Megan was correct and he stepped up his attacks in what I personally believe was a campaign to drive her away from the show. It got to the bullying or hazing level. That's when Bob Greenblatt stepped in and white-knighted Megan, since he was a big fan of hers after seeing her in the LA run of Wicked. There were a couple other little toxicities floating around the production at the time and Bob cleaned house on all of them. He also became Spielberg's public enemy number one, but Bob pulled rank as the head of the network.
Shots were fired when Jamie Cepero was not asked to return as Ellis--Bob Greenblatt made the case that the character was mocked and loathed in just about every write up, and was even the subject of some very negative articles about the show. Focus groups were scathing on that character too. Ellis, however, was Spielberg's favorite character(!). When Bob finally won a consensus that Ellis had to go, Spielberg was defeated and his interest in the show (and his attacks on Megan) waned.
Bob did what he could to right the sinking ship by bringing in a new runner and rehabbing Megan's character into someone audiences could root for. He also thought a major problem with the first season was that Karen Cartwright's successes seemed unearned and hollow (another result of Spielberg's meddling), so he fought to make her arc less preposterous. All good ideas, but too late... by that time we had earned the label of High Camp Trash, and the writing was on the wall.
Throughout all of it Megan was the picture of professionalism and poise. Also really sweet and goofy-fun, in the way of theatre actors.