Climate change wasn’t really mentioned by the Liberals. There was a leadership spill last year where they could have chosen a climate doubter as leader of the party but went with the more moderate Morrison. In practice this means we’ll stick with the Paris agreement (unlike Trump) but probably won’t have a lot of action on climate change in the next few years. I don’t think this issue would have tipped many voters towards Morrison. (FWIW I believe climate change is real).
There are many reasons why he won and also why the polls got it wrong. He was a ‘reluctant leader’ who supported the previous leader (Turnbull) of the party in the spill, so he seemed more like a brand new leader rather than an incumbent up for re-election. He played up the personality angle as he was more likeable than the leader of the opposition (who by contrast was involved with the backstabbing of his party’s previous two leaders and has a dramatic speaking style that sounds fake). The opposition had an overly ambitious economic plan with new taxes and changes to retirement funds that scared people, not to mention housing changes while a lot of people have mortgages. And of course there is the usual left wing being out of touch with people on social issues like gender theory and abortion. A lot of the surprise electorates that went to Liberal were in working class areas.
The polls used to use land lines to call people but now use mobiles, which leads to some sampling bias, but some theorize that the real problem is the sampling companies overcompensate for sampling bias and end up swinging the other way. Plus as you say some people are ashamed to publicly admit to being conservatives but have no fear of voting that way in private. (Accusations of “racism” related to issues of refugees, Islam, native Australians etc. fly as thick and fast here as they do in other countries, especially with the recent violent attack in New Zealand). But there might be a way to salvage the concept of polling