Waitlist at UCSB and BU???

In the past week I got waitlisted UCSB and Boston University. I have a ton of great options still, but I was a little surprised as my guidance counselor had told me UCSB was a most likely 50-50, and BU was a viable. He was shocked to find out I hadn’t been admitted to either. What are the odds of getting off the waitlist? Also is there anything in particular that explains why I might have been waitlisted?

Any insight you could give me would be great regarding the pool or things that might have stuck out in my application would be really helpful.

Info about my application:

ACT score: 30
Subject Tests: US History - 800
AP Scores: US History - 5, US Gov - 5
GPA: 3.97 UW, 4.24 W
Senior classes: AP Euro, AP World, AP Psych, AP Spanish, Honors Calculus, Honors English, Physics
Class Rank: school doesn’t rank

Gender: Female
State: NJ/ CA ----- my dad lives in Cali and I live there part time, so I am paying in-state prices (kind of a confusing matter, but basically they evaluated me as an in-state applicant.)
School type: rigorous private school
Income bracket: around 200,000
Hooks: none

LOR: strong (for BU)
Essays: strong (both)

Extracurriculars (leadership in parenthesis)
Tennis team - 3 years (captain and assistant coach)
School Charity Fashion Show for local elementary school - 4 years (chair) - around 200 hours/year
Camp counselor at overnight camp - 3 years - paid
Youth group (membership outreach chair)
Yearbook (editor)

This is a complete guess because who knows what unsavory thoughts lurk in the minds of admissions officers. For BU, the ACT could be a bit higher. Apparently they had a spike in applications this year. Maybe better ECs? But who cares? Admissions in the UC are insane because of the number of applicants. I think UCSB is up past 70K. You say you have great options. Why waste mental space on these places that waitlisted you? Focus on the very smart places that accepted you and think about where you want to go. Admissions decisions cannot always be explained, and you should be thinking about where you want to go.