Yes, and that is one reason authors often promote the first book in a series.
A promotion can introduce Book 1 to readers who have never encountered the author before. If those readers enjoy it, some may continue to later books in the series.
Read-through does not happen immediately. Readers may download the promoted book and wait days, weeks, or even longer before reading it.
Factors such as the strength of Book 1, series pricing, the transition to the next book, genre, and the number of books available can all influence how many readers continue.