It's been just two years since the CAA has been passed. It takes time to implement things in real life, unless you think this is a video game?
Himanta Biswa Sarma, arguably the tallest leader of Assam, has repeatedly recommended CAA in his speeches, as have other BJP leaders of Assam. Assam BJP was divided over the CAA (Sonowal never openly supported it), others did. For anyone who remotely knows Assam, it was always considered suicidal for a party to openly speak about Bengali-Assamese Hindu unity. BJP flipped the narrative on its head. The opposition had been constantly trying to ignite passions between Bengali and Assamese Hindus. The state government nipped it quite well. Contrast that with every Assam government of the past.
Learn why the Assam NRC failed first. The supreme court appointed panel was predictably a failure. Ranjan Gogoi and Prateek Hajela targeted Bengali Hindus to muddy waters. BJP had been pointing that out since the beginning. BJP made Gogoi a deal to either give a favourable Ram Mandir verdict (happened two days before his retirement), or they'd expose him. That pretty much explains the verdict, which was so uncharacteristic of him, given his past. His buckling to BJP pressure pissed the opposition, followed by a flurry of #METOO allegations on him