Why was a denied by UCLA and UC Berkeley?

The other day I was rejected by UCLA, and last night I was rejected by UC Berkeley. I was very disappointed because UCB had been my dream school throughout my four years of high school and I wasn’t even waitlisted. I am making this thread because I want to hear as many opinions as possible as to why I was denied.

I have:
4.06 unweighted and a 4.57 weighted GPA at a prep school
5 AP classes
35 ACT composite score
800 SAT Math level 2 subject test
760 Physics SAT subject test
790 foreign language SAT subject test
Fluent in foreign language and lived in foreign country for about half of life
Taken an engineering elective for 3 years (was also member of inaugural STEM program at my school)
Attended STEM camp at local university over the summer
President of math club, treasurer for international club
Played sport for school team and club team all through high school
About 90 volunteer hours
Member of science olympiad team that advanced to states
Member of NHS, science NHS, math NHS, and Cum Laude
Work experience as a tutor

I applied as an out of state student to both UCLA and UC Berkeley for mechanical engineering. For the first essay, I talked about my international experience and how the UC schools could help me connect with the business world of my home country. In the other, I wrote about my consistent love of building throughout my life (might have been slightly unoriginal). Although I did not receive any professional help for my essays, I did have my college councillor read them and give me feedback.

I know I listed mostly positive qualities and accomplishments above, but I do not mean in any way to be pompous or arrogant. I am just genuinely curious as to why I was rejected and not even waitlisted. I understand that both UCLA and UCB are top tier universities (especially for engineering) and many of the applicants turned away have similar stats to those that were accepted, but I want to know if there were any particular factors that I did not take into consideration when composing my application. I have also heard a lot about UCB’s shady holistic admissions process, so any insight would be greatly appreciated. Feel free to ask any questions. I hope this thread might benefit others in the future. Thanks!