What other factors can propel a CEX growth?
Their generosity. 
So, aside from being not strict with KYC implementations, the airdrops that they're doing through launchpools or launchpads are the ones that are making them more popular. The more money they distribute to their bigger distributors and depositors, that's how they're showing generosity to the users that are loyal to them and have trusted them with their funds.
Clients need to feel like they are cared for so any cex that would have unique features that give bonuses to their clients would definitely have a high chance of growth. Most clients will look for those cex that can provide what they need and more. It will be your cutting edge against other cex. Of course you need to find the line between giving bonuses and not losing money in the process.