That's even more daft though you need to be able to prove someone broke a law if you want to charge someone else it will just get thrown out - you can't just charge someone with something for the sake of it.
You've just described what happens hundreds of times a day in the US to people who can't afford a couple of million for lawyers, or even to spend a few days (let alone in many cases months*) in jail, so plead guilty to "lesser" offences because it gets them out of jail without realising how it means the next time they're arrested on a bogus charge it's going to be even worse.
The US system is frequently very much about charging people with everything they can and hoping that even if the person isn't guilty they'll plead, or charging with everything they can so that the Jury (when it finally gets there) can have the option of deciding what the person was guilty of.
In the UK it would be like charging someone with both death by dangerous driving, death by careless driving and speeding in the event of someone dying in an accident where the vehicle was speeding (IIRc death by careless or inconsiderate driving was bought in because death by dangerous driving is far harder to prove).
Rittenhouse got bail despite killing people, when it's common for people who can't afford to post bail to get stuck in prison for months/years before trail for far lesser offences.
That's not exactly the system treating him harshly.
*Cash bail is an abomination when combined with plea deals and an extremely slow legal process that enjoys locking people up, as it means you often have to choose between spending months/years awaiting trial in jail, or pleading guilty to something you didn't do.