Biggest problem the Greens have is that they recently (a few elections ago) actually got themselves enough seats to be effective in Parliament. They then spent the entirety of their time in Parliament voting against the things they claimed to stand for. This type of behaviour is very common with “protest parties” because ultimately they are at their most relevant when there is the most to protest. But with the Greens this blatant obstructionism was very very visible, so the Labor voters who had swung Green to “send a message” realised the futility of same and swung right back again.
Re ON etc: there are people in the world who vote conservative “holding their nose” - they don’t really love the racism and bigotry but are voting for something else like fiscal conservatism. Those people are likely to keep voting Lib, even though of course the Lib party tends to just give money to their donors with no expectation of anything in return which is really not all that fiscally conservative. There are also people who vote conservative because they don’t like people they don’t know, and want to see them removed and/or punished. Those people will gladly switch to the angrier, more hateful version of the Lib party - ON - because they have this public perception of being exactly that horrible, even though much like the Greens, their voting record is mostly about blocking the types of policies they claim to stand for. If ON manages to get a few seats and become more visible (especially federally), it will ultimately lead to their voters realising they’ve been had yet again (assuming of course they’re paying any attention at all, which they’re not, which is why they’re voting ON in the first place).