When Binance first start it didn't have highest trading volume and IEO yet. What they had at that time, easy to use and friendly website designed, trading terminal, enthusiast support team, good strategies. I remember that time Polinex and Bittrex were biggest exchanges, they refused my KYC dozens times, while Binance completed it in a day. Because of that, now Binance is the biggest exchange.
Binance KYC is the best here. It's almost instant as long as requirements are met. KYC verification isn't also compulsory, it's only needed for increasing daily limit and withdrawals of fiats
I believe that this is a good reason indeed for a lot of traders to trust Binance.
It's easy really, The reason we trust Binance because of it's rating and popularity. There's just a slight chance that BNB is turning against us. What if Binance is a scam? Well, If it is. Then it will shake the whole crypto world. It's like one of the main foundation of a building. Remove it the building goes tumbling down. Why? Because binance right now is the #1 coin and they own CMC. So if they are not legit. Why bother buy CMC? To get more attraction and scam people on the long run?
Actually, re: Binance owning CMC, this issue did raise some concerns about CMC losing their credibility.
Re: trust, I totally agree that security is a very important factor indeed.