As a hypothetical example, imagine if Apple had sourced the M1 chip from a third party which it now proposed to buy. There would be intellectual property at stake there too. This case is no different.
And indeed, in the Apple hypothetical you could well expect consumers to be better off and for exactly the same reason: if Apple purchases an input (the M1 chip) from a monopoly supplier (the hypothetical non-Apple-producer), vertical integration removes one monopoly markup.
I do not know exactly what will happen in this case, but it seems like Amazon's proposing to buy a single studio is very unlikely to result in harm to consumers.
The copyright issues do not make the case relevantly different.