Hubby and I definitely have a closer bond with me having other partners. It's partly because he isn't the only person in my life, which means he gets a break from listening to me and supporting me when I'm having a hard time. That might sound like he's harsh, but he isn't; he doesn't like long conversations with anyone, and my mental health issues can be a pretty big load for one person to help me carry sometimes.
I'm also happier when I have another partner, and that happiness carries over into my marriage. When I'm happier, so is Hubby.
It helps that he also gets somewhat turned on by knowing that another man wants me and fucks me, but Hubby's the one I come home to.
Establishing the open marriage we started with, and fine tuning it into our current arrangement in which I have polyamorous relationships and he sticks with only me as a partner, hugely improved our communication with each other as well, because I insisted on having possibly more discussions than we needed to have to set out boundaries and agreements. With the open marriage model, both of us wanted to keep the marriage the top priority, especially for Alt and Country's sakes. I don't do hierarchical poly, so I wouldn't say my marriage takes MORE priority than my other relationship, but it's still important to me and to Hubby that the marriage be not only functional, but good and happy. In order to make that happen, especially at the beginning, we *had* to communicate about boundaries and expectations, and that was something we'd never done even though we'd been together nearly three years by that point.
So yeah, I would say my being polyamorous and having other partners has definitely benefited my marriage. Sometimes Hubby puts on his asshole hat (that's his phrasing, not mine) and things get rough for a while, but we're now able to eventually talk it out and make changes, something that we rarely successfully managed before the open marriage.
One thing I make clear to Hubby and to any other partner I have is that I don't consider anyone *more* important. They're important in different ways and bring different benefits to my life. Hearing that helped Hubby wrap his head around the whole thing and not worry as much that I might leave him for someone else. Maybe telling your husband something similar would help him?