Right, because those don't have any carbs.
Also, I guarantee I'd gain weight on that diet without portion control because I'm a natural hog who is optimized to stock up for the long, lean winter that's coming any year now.
More likely you just lucked out with a higher than average metabolism.
You'd think this because of the horse shit that was spread throughout the media and medical community through the 90s and 00s, but it isn't the case. While I've almost always been skinny, I was consious of my health and diet since I was in college and put on 20 lbs the first semester of freshman year. After that it was eating egg white omelettes, skinless chicken breasts with fat free dipping sauce, and oatmeal as the AHA recommended, all while doing cardio and lifting. And the entire time I was hungry and miserable because I love to eat. I want whole pizzas and giant plates of spaghetti and triple cheeseburgers.
Once I hit my early 30s, I started gaining weight again despite maintaining the same, successful routine I had for over a decade. When I had kids it got worse and I thought "fuck, guess my metabolism is just done" and I started aggressively calorie counting and portion controlling with moderate success. Except I was fucking hungry all the time because I still wanted to eat like a fat kid. Eventually I found keto and Atkins after watching the Fat Head documentary and that was a turning point in my life.
Over the past 7 years, I've tried a lot of variations of keto. All were successful, but the carnivore versions have been the best. I can eat as much meat, eggs, and dairy as I can handle and still never gain a pound. I even do fruit when it is in season and regularly eat tomatoes and avocados. The only time I see weight gain is when I consistently eat bullshit for multiple days over multiple weeks. Due to family stuff, I currently am 5 days on/2 days off the diet and still haven't gained any weight despite feeling like total shit the morning after eating an entire large pizza alone.
I have backed off my "low carb is the only way" position from a few years ago, despite thinking it is the best way. I am more than happy to acknowledge that you can achieve fantastic results with calorie restriction and portion control. Ultimately, though, I don't think those types of diets are sustainable simply because most people can't live the rest of their life on a starvation diet. I know I couldn't, and that is what led me where I am today. I was just tired of being hungry.