Scientists just love to be corrected
It's how they roll.
A team of astroboffins from ETH Zurich's Institute for Astronomy have discovered an enormous black hole that shouldn't exist. The black hole is one of the largest ever recorded, the equivalent of about seven billion the mass of our Sun. It resides in the heart of galaxy CID-947, which is around 11 billion light years away, …
which is why such massive holes on normal galaxies aren't seen closer to Earth
It don't see it.
That kind of reasoning applies to evanescent objects, like early-universe hypernovas, but black holes have staying power in timeframes of a few billion years.
I don't have access to Science, but my guess would be that we don't tend to see active black holes in nearby galaxies. Black holes of several billion solar masses will easily outlast the rest of the universe - Hawking radiation is insignificant at such sizes, in fact it's currently (and for the very long-term future) outweighed by the gain in mass from the cosmic microwave background.
How do you think Science works?
We don't know something so we come up with a testable (falsifiable) hypothesis to suggest a mechanism for what we observe happening to happen. Through observation we test the hypothesis. If it seems to fit, we have a theory for how the happening happens. If not we bin it and try again. Then we observe an outlier case that challenges our theory so we come up with a falsifiable hypothesis/refinement to the theory to take into account the new observation and then we test it again. If it then fits the current cases we know about including the new outlier data we consider the theory updated and improved if it passes peer review and others are able to repeat the test with the same results. If, as is likely, in the case that in the repeat of the test, often with better equipment, we see something else curious that doesn't seem to be explained by the current, updated theory, we go again. Eventually we end up with a theory/model that very accurately explains and predicts natural phenomena.
"Making it up as you go along" is the magical thinking usually reserved for spiritual or supernatural realms of human consideration that are, by definition, outside the scope of Science.
"Starting from first principles" is the logical thinking that is part of the scientific method of starting investigating a phenomena when you haven't got a clue. And it works!
Which came first, the massive black hole or the galaxy? Seems like the new data indicates the black hole came first, likely from a supercritical clumping of dark matter. You can't form such a massive black hole that early from an infall of normal matter, there is blowback from the accretion disk and jets which limit
further growth.