My husband turned 40 and suddenly became the man I married again

Hi, I?m new here. I create this account because something happened to my husband about a year ago and I don?t know what to make of it.
My husband has always been a good man, and he?s a wonderful father. He also has a great career and very driven to succeed. But after the kids were born his passion for me had waned. He was once very affectionate and flirty and he couldn?t keep his hands off me. We had date nights and would take weekend trips filled with kissing, hand holding and a lot of sex. But after the kids all of that began to fade and it continued to the point that I felt like we were roommates. I kept myself in shape for him and initiated sex often. He would never turn me down but it was lazy. It was basically get off quick and go to sleep. So after a while I just stopped imitating.
This continued for years and I had just grown used to it. I still loved him, I had no desire to cheat or divorce. I just figured this is what happens after kids and I?ll just deal with it.
Then, about a year ago he got a babysitter and asked me if I wanted to go away for the weekend just the two of us. I was shocked but agreed. And the entire weekend he was affectionate and flirty and just fun. He hadn?t acted this way in years. He was a completely different guy and that included in the bedroom too. This may be TMI but my husband hadn?t performed oral sex on me in 10 years and every time he had before he was kind of terrible at it. But while we were away he just did it without asking and he was amazing at it.
This new attitude continued when we got home and a few months after that I started to notice that he had lost weight. Shortly after that he started to look more toned as well. He had gotten a dad bod but now he looked better than when we got married. I won?t lie, I had difficulty keeping my hands off him.
He?s basically become the perfect husband overnight, I don?t know what happened. He says he just wanted to be a better husband but there was no event that triggered it outside of turning 40. Could that be it?
I?ve read that middle aged men sometimes get in shape because they are looking to cheat. But that?s not the case. He?s never cheated or had any desire too. We have lifestyle 360 for the kids and I see where he is. It?s work and home. I also see all his texts since we share an iPad.
So I?m kind of stumped.
TLDR: My husband suddenly became a perfect husband and I don?t know why
EDIT:
Thank you all for the comments I will answer a few common questions.

1. I see no testosterone in the house. Unless he?s taking it at work and not telling me then I don?t think that?s what it is.
2. How did he become so good at oral? He did tell me that before he didn?t like it but now he does. I could tell before he was grossed out by it and that affected how I felt about it. So right there was a change. But that doesn?t explain how the man has become downright intuitive with oral and sex in generally. He has a sense of when to speed up, when to stay consistent, when I?m close and how to get me there. I just don?t know how that happened. That part didn?t happen right away but it didn?t take long.
3. Like I said above cheating really isn?t possible. I always know where he is and have for years. I can track him and so can the kids. He goes to work and comes home. And when he leaves the house it is to the store or his parents and I can see that too. Also, wouldn?t you get in shape before the affair not after it was over? Because I have been hyper vigilant and there?s nothing.

Source.