Your age and the fact that he was a coach on the team does give me a bit of a chill, because he was in a position of both power and vastly more social/life experience than you. The fact that not much happened for a long time could be worse or better - respectful of the huge age difference and your space, or a pattern of grooming by letting things happen so slowly you didn't question it? Nobody is going to know except you and your DH. If it were one of your daughters I'd expect you to feel very uncomfortable with that.
BUT.
(And this is a big but, and it's not excusing it nor is it a get out clause for predatory men everywhere, or indeed men like your DH who seem like good men who behave in a way which is predatory, hopefully unintentionally)
I've known very immature 25 year old men, with poor social skills, who would be at a social and conversational level of a teenage girl and who were too intimidated by women their own age. It's gross, and it still isn't right, but it's definitely something that I've seen anecdotally.
If you've got no concerns about your DH's behaviour since then, he's not controlling or obsessed with your comparative age/youthfulness, there isn't a pattern of 'older and more experienced' telling you what to do or say or wear, he is a good and respectful husband and he doesn't display poor attitudes towards women generally (I assume not as you're still married!)... I'd chalk it up to something that in retrospect isn't the most advisable thing but that you have grown into equal adults with a fair, equitable partnership. And that's a good thing.
I sense that you're shaken a bit by this though. Why is that? Do you feel like you glossed over specific aspects of how you got together that feel not-great in retrospect, or do you just think the changed social perspective these days has made you look at it with fresh eyes?