Probably that channel has a video that went viral, or the content is amazing, and the videos were optimized.
It is possible to gain subscribers swiftly if you are doing it correctly. As a creator, the first step is to determine the content you’re executing for your niche.
Do something that interests you like a hobby, so you have a lot to share. Focus on content and your craft, NOT numbers.
As a YouTube creator, it requires you to learn how to optimize SEO as a technique.
By doing it properly, it can give a tremendous result to your channel. Your videos will get a higher chance of it to get to the suggested search result, more engagements, click-through rates, more views, and eventually more subscribers too.
Optimize your video by strategizing your keyword, perfecting-your-thumbnail creating an enticing title, properly tag your videos, write a good description, and so many more.
Another way to grow your YouTube channel is to buy real subscribers. I usually buy from Instantviews.co. They increase genuine and real subscribers by promoting your video on different online platforms.
Don’t compare your growth with others. Keep on creating videos with the content that you love. Point is You never know when things will work. But focus on the things you CAN control and work your butt off with clear cut goals! Best of luck to you!