People would have known all this in the old days, because they read proper science fiction
In theory one might make synthi-fuel using renewable power, but that's not really on. Most analysis suggests that even the most extreme renewables plans would struggle to deliver as much energy as civilisation uses now. If the energy requirements of the transport sector increased by many times over - as it would if future transport ran on synthi-fuels made with CO2 - there'd be no hope of success at all.
A renewables-powered future might be possible, but it wouldn't have hydrocarbon synthifuel in it. Synthetic energy-rich fuel only makes any sense in a society which is largely nuclear powered, by fission or fusion.
It makes quite a lot of sense then, however: conceivably more sense than using hydrogen, the other widely-touted energy storage method in that scenario. Sure, hydrogen takes less energy to make, but it's much harder to handle and store with any safety - and its low density makes it difficult to use in many applications like aircraft. Hydrogen-fuelled planes would be mostly fuel tanks. Even hydrogen cars normally need to burn the stuff in fuel cells rather than combustion engines to get useful performance.
People in the old days knew all this. H Beam Piper - a man with high-school education who'd have been just as happy writing detective stories for better money - assumed in his sci-fi tales that the spacegoing Earthmen of the future would make "thermoconcentrate" (eg, "energy-rich" as Dorner puts it) synthi-fuels for use in vehicles not big enough to have onboard nuclear power, as other planets probably couldn't be relied upon to have handy underground reservoirs full of almost ready-made jet juice.
Sci-fi fans used to read writers like Piper: now they mainly read about vampire lust, seemingly.
And nowadays - I'm suggesting these things are linked - when a potential step forward in synthetic fuels is announced, it gets reported under the headline "jet fuel from water". When what you're actually talking about - in practical terms - is making jet fuel using uranium. ®