The gloss black trim used by many car manufacturers is a ‘soft’ plastic so prone to scratching and swirl marks. However careful your car washing regime is, they will become swirled over time - more so if you wash your car with a sponge and single bucket of water and dry it with a wash leather, or if you use one of the many £5 hand wash operations.
To remove them, you could try something like G techniq P1, which can be applied by hand or machine polisher. If applying by hand I’d recommend using a foam applicator pad. To hide them, you could use a polish containing fillers - something like Autoglym Super Resin Polish (SRP). You’ll need to re-apply the SRP at regular intervals to keep the swirls hidden.
Once you’ve removed the swirls, if you don’t already do so, I’d recommend adopting a ‘safe’ two bucket method of washing your car with a lambs wool mitt, and drying it with deep pile microfibre car drying towels. As said above, the swirls will eventually reappear, but less frequently with a safe car washing regime.
Another more permanent alternative solution is to get these gloss black plastic trim pieces vinyl wrapped in a matt black vinyl.