Terry
You have raised some interesting thoughts. I've had a few running around in my brain but I haven't gathered enough info yet to support it so at this point it is conjecture
I have no doubt Charles Taze Russell had sexual feelings. He was human, after all! But, I personally think he was neurotically afflicted about these feelings. Because of his mother's influence on him (and Scottish Presbyterian bugaboos about the evil of sexuality) Russell entered the "marriage" with a weird and perverse "prenuptial agreement" never to have physical relations with Maria.
My theory is that both Russell and Maria were busy writers. They worked well together and possibly at times they were alone together. We are talking about people who lived in a very sexually repressed culture that looked down on men and single women who were often alone (just think of how the WTS today thinks that men and women must never be alone, not only for their protection but for appearances sake)
The work was crucial for both of them. But working long hours, sometimes into the night was sure to draw comment. They may have never done anything sexually but if the rumors started they would have to find a way to stop them.
So they agreed to a marriage in name only. This would satisfy the needs of those who were critical of them working alone. And both would be able to as much as they wanted without ridicule.
For me, this provides a reason why Maria would agree to a marriage of convenience. Her reputation would remain clean and she and Russell would continue the work they were so dedicated to.
I suspect that Russell relied very much on Maria and gave her attention due to the doctrinal contributions she was making. It had to be very flattering. Getting a marriage proposal, regardless of the strings attached would have been an honor. On some unconscious level she may have hoped that after time there would be more in the relationship. So she accepted.
They continued to work together, but now the rumors were stilled.
Enter Rose Ball. A young woman. Dedicated to the cause. A hard worker and she got the eye of Russell. And if the story is correct got a bit of his arms and lips as well.
So there was Maria who had accepted this marriage deal, perhaps with the hope that one day Russell would be willing to consumate the marriage. And she sat back and watched him turn his attentionto a young woman in their midst. And not only was Rose the flower in Russell's eye but he admitted to interests in other palces as well.
Maria had to be jealous. His eye and attention was going off to other women while she was only valued for her mind. That had to be a blow. And if this scenario is correct her jealousy may have been what moved her to file for the divorce.
She admitted that she did not think he ever crossed the line and committed adultery. gave up a lot for this marriage of convenience.
If she had any ideas that one day she could expect love and perhaps a family were sacrificed. She could have married someone else and had those things but now it was too late. Divorced women weren't often considered a good catch. But she couldn't stay and continue to watch Russell give his attention to other women while she sat on the sidelines.
Like I say - only conjecture but I think it offers an idea about why she would have accepted this marriage to begin with