s’écroule

Is from the pronominal verb s’écrouler, in fact we should say se écrouler, like in se faire, se donner.

But because écrouler starts with a vowel, the prononciation is pretty hard, that’s why se is shortened to s’.

m’importe

This is in fact a shorter version of importer à moi, which became me importer, and for the prononciation became m’importer