Take what I say as conjecture.
The LCME are what accredit MD schools and the AOA are what accredit DO school. It is all the matter of what route the people making the school want to take. If the school is lacking in research or even strong clinical affiliations (ex. rotations with GME), the AOA standards are far more lenient hence the reason certain schools would choose this route. There could be plenty of reasons why a DO school is open instead of an MD school (doesn't mean they want to do the bare minimum), but in the end it is easier to open a DO school over an MD school. The proof is in the rapid expansion of these schools.
Just because the school lacks these requirements, does mean one will be doomed to a sub-par education. One can still do well on the boards, try to do rotation in hospitals with GME during 3-4th year through elective rotations, and then match into a good residency. It is still possible to start weak and end strong. However, in the end it is better to have a strong start and then have a stronger finish (i.e. strong research connections, and rotations with GME through 3rd year). It is the path of least resistance. You can still be a good doctor in the end if you put in the work and make the connections to get the best out of your education.