Well, Danerys had the ultimate weapons, the most fearsome army in the world, and the love and respect of powerful people around her. She was going to be queen. Jon had a chance to marry her, take a woman he was truly in love with, and together they could have been a great duo. Jon could have reined her in, tempered her anger and arrogance. She wanted desperately the love of the people and saw that the people loved Jon in a way they didn't love her. This is a great bargaining chip in the relationship -- she could follow his example and learn from him and become the kind of leader she so wanted to be.

She lost another dragon and then her best friend, and losing Jon as a lover was the thing that pushed her over the top.

Imagine if instead Jon said "fuck it I don't care if she's a little more closely related for comfort, I'm going to marry her anyways", it would changed everything. As a duo, fire and ice, they would have a really good shot I think at balancing the whole shebang and becoming something great and worthy of the love of the people.

What do you mean by Bran employing strategy across the timeline?