Tell me about your toddlers who regressed socially or verbally… how is this not more looked into?

My son was completely typical until about 2. He just turned 3. He made eye contact amazing, was social, played back and forth, always smiled and happy, great sleeper and eater. ZERO signs before the speech delay or slow progression became noticeable. Anyone else have a kiddo like this? It’s so strange to me looking back on videos he’s completely on track and so engaged.