I ate meat, processed sugar, and dairy throughout. In the past I tried cutting those things out (except meat) and I struggled with weight loss.
The one other factor that probably played a role is that I cut out restaurants.
I wish I understood the mechanism better, though.
You would be shocked how many calories restaurant food has (usually >1k calories in a single dish -- no matter what kind of restaurant -- and probably more in the US). Personally, I would've assumed this is the more likely primary factor for your weight loss (combined with the fact you probably eat less food overall because you only have two meals when doing IF). You could try going to restaurants again for a few weeks and see if you start gaining weight again.
But, if it works for you -- it works for you.
It appears as though cutting out restaurants made a difference but it’s also easy to underestimate the power of having a morning-based feeding window. People are more insulin sensitive in the morning and have reduced appetite (hence everyone saying “IF is easy, it’s so easy to skip breakfast”).
Jokes aside, I feel we all underestimate how much eating out and/or socially forces you to eat more than necessary. Personally when we're cooking, we rarely go overboard. When you eat out, it's so easy to eat more than what you need.