There are 2 fundamental errors with your claim.
Switzerland has a low crime rate yet the 2nd highest rate of firearm deaths in Europe behind Finland (which has more guns). Strangely, there is a strong link between gun ownership per capita and firearm related deaths per capita in Europe.
The fatal dagger to the heart of your argument is the simple fact that Switzerland has one of the lowest overall murder rates in the world - ranked 211 out of 230.
Switzerland's high levels of gun ownership has not resulted in higher rates of overall murder.
The preferred tool of the murderer in your country is inconsequential when you have almost no murders in your country to begin with. Murder is still murder regardless of what tool was used. Would you rather live in a country with .5 murders per capita, but more of those murders used firearms, or a country like Uganda with 11 murders per capita despite them having one of the lowest rates of private gun ownership in the world? There are dozens of countries with almost no or low private firearm ownership that have atrocious murder rates, and there are many countries with high firearm ownership rates (New Zealand being another one)
The fact that access to easier forms of murder in Switzerland has not actually increased the murder rate disproves your claim that Switzerland would be a safer, more peaceful, or better place to live if they had less guns. They are already among the premier of safe and peaceful places to live, with one of the lowest murder rates in the world, yet still have one of the highest rates of gun ownership. Disproving any direct claims of causation between gun ownership and homicide rates.
The entire map of gun ownership rates and homicide rates internationally disproves any direct cause between the two.
There are multiple examples like New Zealand and Norway having high rates of gun ownership yet are still ranked amongst the lowest in murder rates. Even the USA, ranked #1 in gun ownership, has a vastly lower homicide rate than many countries that have almost no private gun ownership.
This is a very disingenuous argument. Black market availability = availability. Illegal markets are not consistent, and a few years ago some Swedish criminals acquired a large quantity of grenades.
The premise of your argument, the idea that access to more dangerous weapons guarantees an increase in murder and assault rates, has already been disproven by Switzerland (and other countries for that matter).
Your point is also illogical because you haven't stopped to think what has changed in the past few years.
What caused the spike in black market activity in Sweden in the first place?
The laws haven't changed.
You speak as though a freighter full of grenades randomly crashed into a Swedish beach and all those grenades just got scattered into the wild and that is to blame for their increasing use in attacks. Because you seem to believe that everyone is a murderer waiting to happen and all they need is access to weapons to make it happen.
The only thing that has changed is a large influx of foreigners who don't hold to Swedish cultural, legal, moral, or spiritual values. They are the ones seeking to acquire weapons by any means necessary because they intend to use them against their fellow citizens.
The fundamental flaw of your argument is that you are trying to claim the only reason native Swedish citizens weren't constantly throwing grenades in the street 10 years ago was because they were incapable of gaining access to them. No, the reason they weren't doing it is because they didn't have a desire to, or they had values which prevented them from seeing that as an acceptable way to deal with their problems. The reason there weren't grenades everywhere in the wild in Sweden 10 years ago is because the Swedish people had no desire to acquire them, because they had no desire to even use them so why bother acquiring them.
It is the influx of foreigners who don't live by Swedish values who are the ones looking for ways to get their hands on weapons because they have evil intentions for those weapons.
You've got things logically backwards. It's not the supply of weapons that's creating murder. It's the demand for murder by the foreigners that is creating a demand for the supply of weapons to commit said murder with. The demand for murder at a rate this high simply was not present in the native Swedish population prior to all this mass wave of foreign immigration.
As an aside; the fact that these foreign criminals in Sweden are able to conjure up a large amount of grenades, despite a total ban on them, should give anyone pause in their belief that gun control laws are the solution to society's ills - given the law's total inability to stop grenades from flooding Sweden and being used in crime when there are criminals intent on acquiring and using them.
As I said, crime/murder is a cultural/social/spiritual problem, not a tool problem.