Mirrorless Full-frame

I don't get this small FF mirrorless craziness.

If you have Leica lenses buy a Leica camera. If you have large FF lenses buy a DSLR. Now this makes sense to me.

But why buying a FF mirrorless camera to use with a large lens? Who will use a 24-70/2.8, a 70-200/2.8 or a 120-300/2.8 with a small mirrorless FF camera?

There are almost none small FF lenses that would benefict from a small FF mirrorless camera. OK, Pentax as a few and Canon just released one but they use DSLR flange distance.

That's just my opinion, and opinions come in all different sizes and shapes.

Regards,
Luis