Bacteria have thrived for billions of years because they can adapt to many different conditions, and because of their skill at reproduction (they breed quickly).
Bacteria can live anywhere, and reproduce really fast.
Two characteristics that helped bacteria survive on Earth for so long is that they can adapt to many different environments and how fast they can reproduce. Bacteria can basically live anywhere, and reproduce as a really fast pace.
They reproduce very quickly and have the ability to adapt very fast.