Toledo fell into T4. (I'll be curious about that story--big fall in 3 years)
It's a pretty straightforward story.
Toledo was gaming the system with the US News numbers. Basically, if you had poor GPA and LSAT, they put you in the transitional program, or only admitted you to the part-time section.
Now, US News includes part-timers in their ranking data. So, Toledo lost an advantage there.
Also, these things snowball. To a degree, the US News rankings become a self-fullfilling prophecy. If your school makes it to, say, #23, students who weren't interested when it was #49 are now taking a look. When Toledo was 2T, some folks who would not have otherwise considered it started thinking about it. When they slid to 3T, fewer people considered it. Dropping into 4T is really bad.
The rankings are imperfect, but any time you fall into a group that includes all the very worst law schools in the country, that's going to look bad.
A 2nd tier school usually draws folks from all over the country. The 4th tier schools are going to basically be commuter schools. Figure OSU and Cinci are better and are also state schools. CWRU is better, and only 2 hours away. Almost nobody is going to leave, say, the Cleveland metro area to go to Toledo since they can go to CWRU, and if they can't get in there, they can just go to CSU.
Even Akron is ranked higher than Toledo, now. This is bad and the Law School really needs to get a hotshot dean to pull them out of this death spiral.