Why did I get declined by @CapitalOne Venture X? #personalfinance #creditscore

Applied for the CU Capital One Venture X and was surprised to be denied. The reason for denial was I've opened too many credit cards in 24 months. I've opened 3 CU, or credit utilization is 3%, credit score is above 800, and cards are paid off every single month. I did call the reconsideration line, blah blah blah blah blah, still denied. For the record, I was super polite to the agent. Before I go to 1, 2, 3, First of all, you should always be polite to the agent or any agent for that matter, because they're all human beings on the other side. Number 1, length of your credit history wasn't mentioned here, and I'm guessing it's probably a shorter length. Number 2, balance between your income to living expenses to your available access to credit cumulatively. Number 3, the stress test method. If you max out every credit card you have, will you be able to afford life? And if the answer is no, they're going to decline.