Re. Kate, I imagine that she was one of at least a few who attended St Andrews with the intention of bagging a prince. She became the successful one, so her backstory (along with the machinations of her mother, allegedly) is the one we know.
As for her introversion and work shy nature, I’ve followed her story a long time and I can’t recall the source, but she is supposed to have once said that she admired and wanted a role like the Queen Mother. A supportive role rather than the main attraction. To be admired and beloved by the nation for who you are rather than the work you’ve done. Which if true, explains the very long game she is committed to. It’s nice to think their life is a fairytale love story but I imagine there is a lot we don’t know about their dynamic. I think the Prince is well aware that she and her family can be trusted for discretion and loyalty (minus a few “leaks” to media during the waity katey years) and that must be a big foundation of their relationship.
Her popularity did begin to rise as they started doing more engagements and as she took on events that highlighted her glamourous or sporty/youthful side. She has become somewhat aspirational in terms of her image, I wonder if people would feel the same admiration towards her if she perhaps looked less impeccable. Image is a huge part of her appeal, as is her ability to follow protocol. People also softened to her as she had children and supported charities relating to kids.
It’s interesting how things evolve as time goes on. Just some of my observations over the years.