Yes Yoko went after Paul first, but he was not interested so she stalked John instead, she never could compete with Jane Asher, but it was a no brainer that John & Cynthia were just a marriage of convenience, so he became her target instead. Linda was always after Paul, not John, long before she met Paul she told people she would marry him someday. John and Linda hated each other, I remember a story that once John lunged at Linda and tried to strangle her during Beatle negotiations.
Linda & Yoko were basically groupie stalkers, and managed to snag them when they were both going through a lot of emotional and business distress.
Yoko was always a fraud, it is a big lie that she met John after meeting him in an art gallery, that whole story was BS started to promote her image as an artist, she had been stalking Paul briefly & then John since 1966, showing up where ever the Beatles were etc, she did this at her husband at that times urging no less, because John could get her attention and elevate her BS artistic career. Sadly,It eventually worked.
Linda was a groupie who used her career as a photographer to bed rock stars, but Paul was always her target & she too managed to get close to the Beatles with the intention of seducing Paul. At that time Linda, though not beautiful, or even pretty, was well put together, and somewhat attractive, she wore her hair parted to the side & wore make-up and looked attractive,(she let herself go completely once she bagged Paul though) like Paul she liked art, music, and pot, so they had common interest & once Paul & Jane split she really went after him.
I do not think Paul would of married her if she was not pregnant & if he was not such an emotional wreck at that time. I think he was probably still hung up on Jane at that time, but Paul did love Linda or at least he grew to love her, although I see her as an enabler to Pauls drug use and boosted his already large ego, she was very loyal & dedicated to Paul, and did whatever she could to make him happy. She grew on people I think. I personally liked her for animal welfare causes, she was the most vocal and dedicated celebrity to that cause.
Between Linda and Yoko I definitely like Linda best, Yoko is a fraud and always has been, she and John got together during his worse drug phrase (heroin), they stayed together mainly for publicity, when they broke up most of Johns friends said he was happiest with May Pang, but he got back together with her when she threatened to kill herself & who knows what else she threatened to do, Yoko is incredibly manipulative & still promotes the "legend" of John & Yoko, but many do not know that she secretly married someone very shortly after Johns death.