Hello. As I understand the Israelites on mount sinai only heard the commandments but didnt see Hashems finger of fire inscribe the tablets. Why is this? And why did Moses write the second tablets instead of God rewriting it?

A monotheistic God obviously has no physical body or attributes, so even a term like written by the "finger of G-d" (Shmot 31, 18) is not meant to be taken literally. Accordingly, to "hear" G-d is miraculous enough, but they didn't "see" Him writing, because there was no such action! The Rambam (Maimonides 1, 65) and Kuzari (1, 89) explain that just as He created the world through the verb "saying" (Breishit 1) but it's also termed that His fingers (Tehilim 8, 4) made creation, so too He "said" and the tablets were made, as if it were, by "His finger". After the sin of the Golden Calf, we received, as sort of a punishment, a lesser level of tablets, written by Moses (Shmot 34, 1).