I'm going to hazard a guess that you applied to both the Case UP and CCLCM. If you did, then that is a big part of the explanation. I think I've mentioned before that CCLCM has its own separate admissions office. It's not just down the hall from the UP admissions office, either. Our admissions office is physically located on the CCF campus, not at Case. So if you apply to both programs, your application basically has to undergo two separate reviews on two separate campuses here and at Case. The two admissions offices do talk to one another, and that adds to the time too. Although their admissions decisions are separate, they try to coordinate the applicants' interviews so that if you get invited to interview at both programs, you only have to come out here to Cleveland once. Unfortunately, this all means that it takes longer for your interview invites to get sent out, since both programs have to evaluate your application before either one or both will send you an invite.
In answer to your second question, yes, it is definitely possible to be invited to interview at one program and not the other. I am not really sure which program will give you a better chance of being invited. On one hand, we have a lot fewer interview slots versus the UP, but on the other hand, we also have fewer applicants. According to the Case admissions website statistics page, last year about 15.5% of applicants to the UP were interviewed, while about a third of applicants to CCLCM were interviewed. So when I applied, it looks like the UP interview was the harder one to get. But keep in mind that because CCLCM is such a new program, the numbers change a lot from year to year. Already, a lot more people have applied here this year compared to last year. Also, this year, CCLCM will be interviewing far fewer people compared to last year (closer to 250 versus 371 last year). So I'm not sure what the new numbers will be, but it's definitely going to be statistically tougher to get a CCLCM interview this year.
I feel for you current applicants. Every CCLCM application season so far has been more competitive than the one before it. The thought has definitely occurred to me on multiple occasions that if I had waited one or two years to apply to medical school, I might not have been able to get accepted here.