See it this way: everyone knows Italian debt at 140% of GDP is unsustainable. Successive governments have promised again and again to do something about it, but then each finds a reason not to follow this promise. The Italian state is leaking money in all corners with many politically friendly businesses making huge gains at the cost of taxpayers. The default is mostly inevitable if there is not finally a serious attempt to address this issue.
Successive Italian governments have asked for mutualised debt - while increasing the national deficit and debt further each year. It would be crazy for any other government to give Italy a blank check and say "okay take whatever loans you need, wecll guarantee it". It means you are consciously taking up the risk of default for yourself while having no way to stop overspending or fix the underlying systemic issues. This means Italian governments have even less incentive to change the horribly corrupt and broken system.
That other countries say no is not a decision against the Italian citizens. It would be irresponsible towards their own citizens to take this up without some kind of real guarantee that Italy will finally fix the systemic issues, because the past 20 years of promises have been broken.