I think it all comes from the herd mentality right from their JEE days. Afaik all of them did well in JEE and got into good colleges like NSIT, DTU etc. And they're very good at following a set framework of learning and teaching like solving a bunch of MCQs, leetcode questions etc. But many of them would struggle in areas which require innovation like building software in small early stage startups. That's the reason all of them are also from big corps like MS and Google where the workload is relatively less compared to startups and allows them to keep doing what they're good at - following a set path of familiarity. In this case DSA courses. Because they know that's what is in demand. Many of them would've made courses on cracking JEE before their MS/Google days.
Also heard that the Nishant guy was gonna get fired if he didn't resign so there's that. Bunch of clickbaity videos to build their social presence and make money off students and fresh grads.