This is the week after Obon, so everything dropped. Fire Emblem's drop is in line with the rest of the top 10.
The launch of Switch Lite should easily be above 100k for the Lite alone in that week, so Switch software should naturally see increases across the board. Depends on what you consider a big spike, but Fire Emblem should see at least some boost; most of the benefits will go to the usual evergreens.
When I say "falling" and "spiking" I am referring to chart position. The raw numbers put this FE at 221k so far. Fates sold about 100k more during it's first week alone in Japan. At first glance it seems like Fire Emblem has lost some of its base in Japan. I am wondering if they are actually just waiting for the Lite edition in order to get Fire Emblem.