I am seeing some talk about Zoomers and religion, so I thought I would chime in. I don't know if Christianity is in decline with Zoomers as much as that data suggests. This may be anecdotal, but there were several major Zoomer revival events on college campuses a few years back, so it might not be as great of a decline as you said. As far as Zoomers being atheists, I think, like you said, they didn't go through atheist phases. I was unique in that I did, and I watched atheist YouTubers, but most Zoomers probably just don't believe and at most watch atheist TikToks.
I think COVID is an interesting thing because I was basically in lockdown most of my life. It made me resent my mom and her form of Christianity. I grew up watching Joel Osteen and a lot of the sort of snake oil prosperity preaching, so after I revolted against my mom, I figured, Oh, if she lied to me about Santa and the Easter Bunny, why not religion? and then watched YouTube videos like those Sam Harris debate compilations, and it affirmed what I was thinking: if Christianity was so good, why is my mom such a hypocritical and terrible person? I thought my mom's horrible example of a Christianity represented Christianity as a whole when I couldn't be more wrong, so I think if you are stuck with Christian parents you hate, then you might revolt, but if you had good Christian parents, you might stay Christian.
After my atheist phase, to make a long story short, I started believing again and listening to Christian YouTubers, and very quickly I realized that my mom is basically what the Bible condemns. She's narcissistic, grudge-holding, almost never forgives, constantly envies others, lies, and she ran the family instead of putting my dad at the head of the household. She also cusses all the time, hates other people, etc. So I realized she didn't represent Christianity like I thought she did, and I was letting her bad example turn me away. when in reality she didn't represent Christianity at all. You can find bad apples in every religion, and she was like a rotten apple that I thought represented the fresh fruit that is Christianity. This is an issue that atheists use to justify their atheism: "My mommy was heckin abusive and a Christian; therefore, all Christians are bad." It's a stupid argument, and it's frustrating seeing people use it. The truth is most Christians are good, and narcissistic people don't represent Christianity properly.
So really, I should have never left the Christian faith in the first place. I think if my mom was good, I most likely never would have become an atheist or had that cringey phase of being a complete fedora-tipping atheist leftist, but instead of actually reading the Bible and taking us to church, Mom just taught me it's God when good things happen, when bad things happen, it's out of our control, and we are not allowed to question that fact or anything else about Christianity This poor theology and parenting made me an atheist, and I'm sure it made plenty of others leave the faith. If Christianity was just a free money hack and praying for good things to happen, why would I even care about it? If good things never happened to me, that would make her theology moot, but later I realized Christianity is not about only good things happening and praying for money.
so after all of this I eventually came back to faith. I don't go to church, so you are right that Zoomer Christians are not as devoted as past Christians were, but I am still somewhat of a religious guy. I know it's autistic that I used YouTube to watch stuff about religion rather than books, but it is what it is; I will eventually start reading books. Also, I have noticed on the topic of decline that YouTube's influence over the youth has massively declined. More people get information from TikTok and Twitter rather than YouTube now, So unlike millennials watching Amazing Atheist, Zoomers might watch a trad Christian TikTokers, but that's a different topic. On the topic of atheism, I have noticed many atheists also had bad Christian parents like myself. So I'm sure that plays a role in both Zoomers and millennials leaving Christianity.
TLDR: I don't think Zoomers are as atheistic as your poll suggests, and I am a former atheist Zoomer turned Christian. I also think parents can influence a child's religion based on how much a child likes their parent.