Don't feel bad. UCSD tends to recruit residents based on what those residents can do for them to get a bigger name.

so painful to not match at a place where you envision yourself

Totally understand. Some of this stuff is "knowing the tea" which you only find out later as a Derm resident. Often it's a function of the faculty at a particular derm program or a chairman. It's ok to feel a little bad because the power dynamic between derm clinical faculty interviewing and you is very much tilted towards them. Don't take it personally. It's not something in your hands to control.

sending virtual hugs