I don't buy that the extreme drop off is just because alt-righters didn't like TLJ. Sure it's a factor, but I think it's more that the majority of people (according to Rotton Tomatoes) did not like it. The other factors is that it was released over Memorial Day (whose best weekend ever was just under $140 million by a POTC movie), the apathy and bad press caused by fans not liking TLJ and the general direction of Lucasfilm movies (All other Star Wars films have Audience/Critics are within 10-15 points, TLJ is close to 50 points), the stories coming from Solo production tanked interest and hype (Alden needing an acting coach and the firing of directors who had directed well liked movies like Lord and Miller had the biggest news), and finally it being the 3rd "tentpole" movie in a month (following Avengers: IW and Deadpool 2). I'm single, I don't have a family, so I can see a movie for $10-$15. Families (2 kids and 2 adults) need to drop at least $50.00 in Nebraska, but even more in other states.
I believe if they would have kept the December release schedule, it would have performed better.
Chart of Star Wars Rotton Tomatoes scores (only one outlier):