There are several online yoga videos which claim to teach you everything about it and even go as far claiming that it will enable you to teach others, these videos are on different online platforms for everyone to see and are completely free to watch, if you think that you can become a yoga instructor just by watching these videos then you are absolutely wrong, in this age of free learning it is still as important and relevant to enroll yourself in a yoga teacher training program, yoga teacher training program are extensive and these are different from what the normal yoga sessions are like, you cannot take yoga sessions for a while and think that you are in place to become a yoga teacher, for us it was Marianne Wells Yoga Retreat that taught us different yoga practices and philosophies in detail.
As a student you might enroll in a yoga class and your goal might be to lose weight or have a better body or even clear mind, but when you get enrolled in yoga teacher training program the approach is very different, you are not there to get the benefits for yourself rather you are learning the skill and that is not just limited to postures and movements, for some yoga is a religion and if you go into detail and start reading its history you would know why people take years to master the practice.
As a basic trainer you need to have the right guidance, even if you have taken the 200-hour training program you still need a mentor on your side for you to take things to the next level, because on paper it is enough to let you be a yoga trainer but when you want to be the best you need extensive training.