That is EXACTLY what is supossed to happen. Google runs a SE with over 5 billion URLs - if anyone tells you, or told you, that a transition was seemless and instantaneous, they lied.
To explain why, Google has this flow:
1. Crawl the old site - once it finds 301 redirects, it kills the old site and has no data on the new site yet.
2. Google crawls the new site, and starts to apply the old sites criteria - this is NOT, repeat NOT instantaneous.
3. All the "pre processed" signals are applied from the old to the new site.
22 days is a pretty short time to see things come back better, and I'd thank my lucky stars!