Community moderation 101:

Topics that directly affect the community will attract more attention by said community.

Topics that contain tropes will perform better than ones that do not.

Outrage & shock will outperform Tropes.

Taken in order:

Random crimes like car break ins get discussed as a warning to others, then celebrated when the perpetrator is finally caught far more than crimes that don't directly effect people on platforms like Facebook but far less on platforms like Twitter. Demographically those crimes are almost never evenly distributed in the first place. Where I live car break ins are 27yr old white junkies on average, across town not so much.

Who discusses crime online also varies by demographic and it mostly tends to be the poor and the upper middle class when a crime is committed somewhere unexpected.

The tropes kind of write themselves these days. Any time you see security video of a gas station robbery the ones where the assailant doesn't know how to hold the gun properly will always outperform one that is less colorful. Bonus points if they obviously have more gold jewellery than the cash value of the take from the robbery.

Outage and shock has also become a self-fulfilling prophecy of sorts as well. In areas with very low case close rates it is much easier for things like the assaults on elderly Asians to happen because it is unlikely anyone will ever be punished. It also means that it is a good bet that intimidating or eliminating a witness gives better chances of not being caught by the cops. Again, demographics of who is doing this vary from place to place a little, but less than in the previous example because serious gangs are usually a prerequisite and those tend to have very little ethnic diversity.

Which platforms have more or less of this depends greatly in what the platform is primarily used for.

Twitter is for arguing politics and complaining to the social media managers of large corporations so it sees less than Facebook which is more general, but not as much as something like nextdoor which has a very local focus.

Places like Reddit are also influencing this as well. When popular sites start issuing ban warnings and perform admin removals over links to government issued crime statistics it motivates people to post individual examples as news to that platform and creates Streisand effect additional discussions of said statistics and the platform's political motivation in suppressing them.

Tl; Dr the type of platform affects the level of attention & the people most likely to discuss crime they were the victim of are far from evenly distributed so neither are the perpetrators. The type and details of the crime heavily affect it's likelihood to be discussed as well.