At first, only some workers were taken out on strike, paper shufflers and service mechanincs not included, and Tesla immediately started to bring in strike breakers from other parts of Sweden. If no one is striking, who do you think is standing by the picket fence as we speak? You should seriously reconsider your sources.
In Sweden, more than 90% of labour is covered by collective agreements. A company like Tesla coming in and breaking all of the unwritten rules threatens the Swedish model is bound to meet heavy resistance from Swedish labour in full, and most unions are members of the same umbrella organisation (LO) so that they can organize across sectors when needed.
While the US regulates strikes and minimum wages by law, it is in Sweden regulated by collective agreements. So, Tesla is choosing to allow strikes against them by not signing it. They're the ones to blame for any action that stems from this decision, no-one else.
Can you imagine the outrage that would come from a Swedish company coming to the US, trying to change fundamental mechanics of the system there without the support of its citizens? Why shouldn't this scenario result in the same outrage and resistance here in Sweden?
The solution is simple, sign the agreement - as is custom here in Sweden.
If they can't conform to Swedish customs then they can simply choose to leave Sweden. Tesla don't want regulation surrounding their workers, so they themselves aren't protected from union actions against them.
PS. They are not targeting a product, they a targeting a company that don't want regulation to apply to their company. The arrogance towards Swedish customs and culture is so nonchalant that the general public currently frowns upon Tesla and guarantees their support for the unions in this specific case. The reports about employees being threatened to be fired and/or have their benefits pulled is probably illegal due to the Swedish constitution that guarantees the right to organize associations, furthering the sense of Tesla not respecting our nation, citizens and customs. Continued resistance from Tesla will most likely result in public outrage.
Now, a completely unrelated union decides to specifically target the product? How is that a work action?