I know for Australia, early lockdowns essentially stopped community spread and once it gets into the population they can be used effectively as a means to force people apart to slow the spread of the disease to give hospitals breathing space.
If you aren't familiar with it, the WHO's Global Influenza Preparedness Plan makes interesting reading. It contains the WHO's "recommendations for national measures before and during pandemics". This document was the result of at least three decades of global experience dealing with outbreaks including SARS and MERS, Beijing Flu etc. Following the 2009 Swine Flu fiasco it was updated and thereafter remained largely unrevised -- before being thrown out of the window by the WHO itself and most Western countries with the onset of the current pandemic.
The Plan has specific recommendations for each phase (Phases 1 to 6) of an outbreak, regarding the appropriate steps to be taken, e.g. at what stage it makes sense to try to prevent altogether or contain the spread, and at what stage trying to do that becomes futile. All the Nordic countries simply followed the Plan, the differences between Sweden and the other three being largely accounted for by the extent to which, by the end of February, early March, the virus had gained much more than a foothold in Sweden compared to the others. In terms of the plan, by mid-March Sweden was already in Phase 6, at which point the Plan specifically says trying to contain the virus is not only useless, but counter-productive; while the other three, and in particular Finland, were still at a stage when prevention or containment by lockdown etc. made sense. So it wasn't that Sweden "refused" to lockdown; it simply followed the WHO recommendations for the stage at which it found itself. The actions that Sweden DID take, such as self isolation by those infected, social distancing, etc., were exactly what the WHO Plan recommended (which, by the way, did NOT include compulsory masks). Regarding the use of lockdowns to protect the health services, the Plan was opposed to doing it on anything other than a very short term basis on the grounds that the cost of doing it vastly outweighed the benefits.
New Zealand's relative success in dealing with the virus is another example of a country which simply followed the WHO Plan for early phase action. They were able to do it because, largely through geography, the virus hadn't yet gained any sort of foothold. In terms of the slogan we were treated to in the early days "Prevent, Contain, Manage", New Zealand were able to "prevent". They then had minor imported outbreaks that they were able to "contain". Here, on the other hand, while the government faffed on about prevention and then containment, we were already well into the WHO's Phase 6.
I haven't really followed the Australian experience in detail, but geography must surely have been a factor there too.