We can Never know the workings of Love. What these two people had, is none of our business. Even if you dig up all the "facts" you can find, you will never realize what these two shared..RIP, both of them.

Yes, you are correct about their marriages. One was married then the other was single; that reversed, and then it reversed yet again.
But as I researched the bio (that I later stopped), their relationship appeared quite confusing and a bit unhealthy.
My concerns about her veracity were confirmed by two professionals. Her surviving former husband does not know how many times she was married (I found evidence of 3 times, but one remains nameless.) She contradicted herself in various interviews on various occasions.
She claimed that Hutton was the love of her life. yet I unearthed an incident of dispute (contents unknown), and she 'ran off and almost immediately got married' (within days, maybe something like a week or two at most). Seems very impulsive and immature. On the other hand, I scoured more than 50 newspaper and magazine articles and interviews in which He sounded impulsive, too, and as though he swung from bombastic to serious and quiet. Of course, publishers took editorial liberties,sometimes a wee bit too much that lost the true tone of the interview.
What I found about Vickers' acting career led me to think she wasn't a raging success, yet she had a reasonable career. Her parents were very successful in their own right, having a jazz band and a few jazz records that did well. (Since Hutton was nuts about jazz, I suspect this was an important common thread in their releationship/friendship.) I remember wondering, though, if later in life she began to embellish (or idealize?) her memories about Hutton to obtain vicariously a sense of success.
She told many many people Hutton was the love of her life, the special one, and how he loved her, too. But I truly doubt it was a deep and rosy as she made it outafter her divorce, it was a long time before she decided to contact Hutton. She learned he was hospitalized, so she "rushed" right down to see him. She said that hospital visit 'was the last time she saw him.' From what little morsels of info I found, he did not die immeditely after that, or for a couple of weeks. So why didn't she contact him again? Single, in love with him, but did not follow up with a simple telephone call, letter, or another visit. Doesn't sound like normal behavior for me.
In those days the movie studios stll told actors whom they were going to date, where and when they would go out in public, etc. Were they really in a relationship or just friends or just two workers out to friendship to satisfy the bosses?
I have no idea.