THE POWER OF KNOWLEDGE

Knowledge is a treasure but practice is the key to it. - - - Thomas Fuller

I have always said that knowledge was power on LOST. Those characters who knew things could control things.

Eloise was probably the one person who knew the most since she had actual working knowledge of both worlds (island and sideways). It seems that she was able to connect to both worlds (and their seemingly same but different lives) as if the island was a gateway or portal to two dimensions. When Eloise conversed with Desmond in the clock shop, the essence of what she told him was that time was predetermined; that Desmond's life was predetermined; that Desmond's destiny was not to marry Penny but to sail off to his own demise. It was this erasure of a possibility of romance in the real world kept Desmond from awakening other characters, such as Daniel, for whom Eloise tried to shelter (in the after life).

Knowledge that the sideways world was a purgatory time line where people could continue to live out their imaginary dream lives is a powerful tool especially when one can communicate back to the living world to manipulate people to keep the fantasy world's status quo.

As most religions teach, what one does in the world of the living has consequences in judgment in the next world. By manipulating the actions of living human beings in the island world, Eloise could construct an elaborate alternative fantasy world where the characters would not need to rejoin and "remember" their old lives which would destroy the egg shell dream family situation Eloise created in her sideways vision.

But how can Eloise be a puppet master in two worlds. She somehow mentally connected herself with Daniel, her son, in both worlds. This theme of having a "constant" may have actually meant the mental connection between the living and the dead. Eloise was a medium who could actually affect events.

She forced her son to give up music in order to study and master highly theoretical physics, including the manipulation of time. Why? Perhaps so Eloise could go back in time herself to stop her young self from killing her own time traveling son. If Daniel "remembered" that his own mother killed him, that would destroy the happy family sideways dream world Eloise had created for herself. That shattered dream would mean that her "heaven" would be gone, and she would either go to hell or worse, just fade away from all conscious existence.

So the stakes for Eloise would be extremely high. It was her manipulation of Daniel in order to control the island which led to the unintended consequences of her shooting her own son. A lifetime of guilt both in the living world and sideways realm had a mother trying to do anything to make things better. In order to protect her vision of her happy family, she would communicate to her living self - - - which led to Widmore's anger and revenge motivations to destroy everyone on the island. By doing so, those souls would not remember or awaken Daniel from his dream state.

One could say Eloise was trying to maintain a complex dream support system for a critically mentally unstable patient, Daniel.  If this was the unstated premise of the series, I think most fans would have accepted it as a reasonable explanation for Season 6 and tie back the previous five years.