But the earth was
The creation of the world was a process rather than a sudden appearing full blown out of nowhere. When with nouns the conjunction is said to be disjuctive. Verse two describes the imperfect condition, ever so much chaos, that the particles were in. For this reason, the waw is perhaps better translated "but".
As much as anything else in creation week, the earth had to be formed into a functioning body. As God superintended creation, he seems to have gathered everything into one place. But without a miracle, nothing but scattered quarks littered space with too far apart to interact. So was the young universe "on its own".
The earth is passively defined with the verb הָיָה , in its usual sense of being or existing. Grammatically it is in the "Qal Perfect"--the simple past in most cases. Chaos was everywhere.