Different audiences respond better to different advertising platforms.
Facebook works relatively well with problem aware, impulse buyers. But the problem is Facebook is the best known and easiest platform to advertise on, which means more and more people are advertising on Facebook every day.
But here's the thing about Facebook and supply and demand. Facebook has a fixed number of users. Users are the "inventory" that Facebook has for you to advertise to. If that number is relatively fixed, and more people want to advertise to those people every day, then demand increases at a faster rate than the supply (inventory/users) and so prices go up.
And since Facebook has so many advertisers on their platform, they don't mind losing a few here and there. If you mess up on Facebook and break any of their compliance rules (either on purpose or by mistake), Facebook finds it easier to simply shut down your account then coach you through corrections.
With Facebook, you can only target users based on their interests. You can target them based on what they are thinking or feeling the second your ad is displayed to them.
The problem with Facebook is that Facebook users don't go to the platform to buy anything or learn anything, they go there to PROCRASTINATE. Thus, when they see your ad they are in a "procrastinator's mindset". And this isn't the best mindset for decision making or spending money.
YouTube is different. First, people primarily go to YouTube with INTENT. Meaning, they are not only very problem aware, but they are actively searching for a solution.
Unlike Facebook where their inventory is a more-or-less static number of user personal profile pages, YouTube's inventory are their videos. YouTube users are currently adding 300 hours of video to the platform EVERY MINUTE.
So where Facebook's supply and demand is more demand heavy, YouTube has a near limitless supply inventory.
And whereas you can only target Facebook users, with YouTube you can target them based on what they are thinking or searching for.
Example: if I want to learn about the keto diet to lose weight, I'll go to YouTube to learn about keto and get recipes. There are 100's of organic keto videos that sellers of keto-related products can place IN FRONT of those very videos.
Meaning, you are not simply targeting somebody who has once expressed an interest in keto (as you would on Facebook, whether it was a true or passing interest, or an interest that was expressed a day ago, a month ago, or sometime last year!). You are targeting somebody who is actively searching for a keto solution this very second.
So you can imagine, with the right offer and copy, it's not hard to attract new customers at a surprising rate.