What is the presence of chloroplast and mitochondrial DNA imply about their evolutionary origin?

The chloroplast and mitochondria have circular DNA, which is like most free-living prokaryotes.

The chloroplast and mitochondria also have smaller ribosomes than eukaryotes, I think it's only 65S compared to the normal 70S, which is common in prokaryotes too.

All these things imply that the eukaryote cell probably adopted the mitochondria and the chloroplast eons ago, and they learned to live in symbiosis, whereby the chloroplast and mitochondria have protection and nutrients they need, whereas the eukaryote cell has energy.

Over time, due to natural selection, the free-living mitochondria and chloroplasts died, but the ones that were incorporated into the eukaryote cell survived til now.