Some brokers block only SPAN margin

Brokers like Astha trade block only SPAN margin, and allow very high leverage for intraday and delivery positions. And they have survived for years. How do they manage their risk? and if they are able to manage it, why can’t brokers like Zerodha compete with them? I don’t think their higher brokerage is enough to mitigate the high risk if they don’t have proper risk management in place.