This is expected behaviour when the folder contains more than 100 files and they belong to different series. If they are in a separate folder for a specific series or there are less than 100 items Sonarr will process them automatically, otherwise you first need to select the series.
I was importing 255 episodes of Looney Tunes freshly downloaded from HBO Max. They removed a ton of them along with several other shows so i wanted to get them in case they decide to remove more.
I just tried importing another 95 and it selected the shows so i got confused and came here to say it works now but now i know why