He threatened to years and years ago yes. He even said he was going to at the end of the season and didn't, but since then there has inevitably been talk and he rejected it every single year. Dude, Mournho wasn't first choice. You don't - or United don't - employ a manager based of past success. Mourinho may win trophies but there are plenty of negatives with his management style, for example: negative media due to his egotistical ways, a style of football that most fans don't enjoy, he isn't for long term (by that I mean he'll leave after three or so years), and relies on plenty of investment. He also doesn't promote from the youth system often at all. Mourinho most certainly wasn't first choice.
I can see someone arguing that Pep Guardiola may have been our initial first choice due to him and Fergusno meeting many times in New York, but other than that Moyes was always the guy. Ferguson sees him as a younger him basically, and he fits the bill on paper. He is reliable in terms of longevity in a job. He is a consistent performing manager in the premier league. He isn't silly and won't get negative press. A figure the players will respect.
Manchester United have a different way of doing things bro. Mourinho is possibly the greatest short-term fix in the world, but he isn't a long-term fix like Sir Alex. United see Moyes as the long term replacement, but I'm sceptical he can be that to be honest. I can understand why they think that, but I think Klopp was the guy we should have targeted.