They do while conditions are ok, it seems like conditions are not ok for these workers hence they pushing for a CBA.

And while lots of companies work without a CBA here in Sweden, 90% of employees are covered by CBAs, so the vast majority are covered by one and Tesla fighting this by bringing scabs (a huge, huge no-no in here) is quite stupid. If they thought a CBA would be bad for business then strikes are even worse, it's their choice now to sign one or not with all the costs associated on not having one.