Prepared for what? It was probably his goal to attain immortality or become a Great One himself. In which case, what need is there for a lump of insignificant meat on this useless rock when the great cosmos await? Heck, for all we know, Micolash may very well have had contingencies in place when he enacted the ritual who-knows-how-long ago, but they all failed anyway, likely as a result of him going mad. But don't fault him too much for it; we're all a little mad in Yharnam.I just think he should've prepared for that scenario.