(re: Sierra and Disney) Disney was not (to my memory) in the game business prior to Sierra.
With respect to your question about whether they tried to “copy us” after they went their own way – that’s not how the creative world works. Generally speaking, it is not uncommon for people to believe they know more than other people. I have no way of knowing what the Disney people were thinking, but my guess would be that they really thought the games they did themselves would be a LOT better than those done with Sierra.
My vague recollection is that Disney lost a lot of money on the software business in the years after Sierra, but did several years later finally start to ship great product.