One that is concerned about a public backlash. I’m not sure if you’re from Australia, but the community is very divided here over this issue. It’s also an issue that tends to be divided by age groups, with older people being more likely to support Israel’s actions or see criticism of Israel as anti-semitism. Classical concert audiences tend to be quite old. With this context in mind, I suspect the MSO received a handful of complaints and incorrectly assumed this position would be less inflammatory. It’s possible that it actually is within their immediate audience, but the problem with making a big public statement like they’ve done is that it automatically puts you on a "side’ in this heated and highly polarised environment.

They should have just spoken to the soloist privately and explained their concerns to him prior to the next concert, instead of turning it into a big controversy. As triggered as some people may have been by the introduction, it wouldn’t have been enough to turn this into a real controversy the way it has become since they cancelled the concert. Like this news story is not actually anywhere near important enough to make World News communities and get outraged replies from foreigners who had never even heard of the MSO before this. It’s the story’s connection to the situation in Gaza that is the big issue here, and deliberately involving themselves in that was a massive PR mistake.

The MSO has already backed down and is rescheduling the concert.

He was cancelled for calling Aboriginal people victims of settler-colonialism in Australia

Extremely unlikely. Australia’s colonial history and its impact on Indigenous Australians is a very common theme in modern Australian classical music and many concerts I have been to, including one just the other week, have conductors or soloists introduce the piece and specifically cite the context behind it. Unless the MSO is significantly different (which it doesn’t appear to be, based on some quick searches of Indigenous-themed concerts) this is not the reason. It was his comments about Israel targeting and killing journalists (what you quoted is not the actual introduction he made at the concert) which led to the cancellation.

It wasn’t actually that broad, he specifically mentioned that Israeli armed forces have targeted and killed journalists in Gaza.

People pay to see and enjoy listening to a symphony, not listen to political opinion.

I guess you don’t attend classic concerts often? It is very standard for conductors or soloists to introduce modern pieces and discuss their sociopolitical relevance. I literally just went to one the other week where the director of The King’s College Cambridge Choir introduced a piece about the massacre, dispossession and forced assimilation of Indigenous Australians.