It may be that the situation is similar to when Giesen took over SCSU. Scanlan, like Giesen, did well with the players his predecessor recruited. Once they graduated, he didn't have much luck attracting new players of the same caliber.
While it is correct that the most successful season in Beaver program history was in Scanlan’s second year when they finished third in the WCHA (2015-16, which was the only season they have ever finished in the top four, I think), they did finish above both the Mavericks and the Huskies in each of his first six seasons. By the fifth season, the only impact player remaining on the roster that was recruited in the Sertich era was Emily Bergland. Scanlan’s first couple of recruiting classes each had several impact players (including Bench, Halluska, Jorde, Kaasa, Mack, and Radke in the class of 2020 and Beebe, DeGeorge, Dowhy, Festherstone, Kampa, Langei, and Passolt in the class of 2021). It was the third recruiting class where things dropped off with only Ellie Moser showing signs of becoming an impact player and her career was plagued by and ultimately cut short by injury. It is that class that would be fifth year players this season, and Bemidji has none (they are the only team in the conference without any). The next couple of recruiting classes also don’t include a lot of impact players (the last two groups that will have five years of eligibility) so that is going to continue to hurt the Beavers going forward relative to everyone else. The current freshman and sophomore classes are both large and seeing a lot of ice time but it remains to be seen if they can have the an impact over the course of their careers that approaches that of Scanlan’s first two classes. I’m afraid their drop to the bottom is not going to change anytime soon.