If you're horrified by animals dying on a farm during a disaster then consider why they are on the first place. It's not a kindness to breed them in to a life of suffering, cages forced breeding only to be slaughtered. The real solution here is to stop the cycle of harming an animal for human pleasure.
(which is also the same reason dog/cock fighting is wrong)
I think a much better question to ask is why should we reframe the topic at hand to not include its root origin? It's kind of like asking why people want to talk about wealth Inequality when you talk about poverty: the two are intrinsicly linked together
How can you think veganism isnt relevant to a discussion about the cruelties of animal agriculture. This type of thing is specifically part of what vegans are fighting against
Rather than relocating animals every disaster, wouldn't prevention be cheaper and a lot more effective? Flooding, for example, is only a surprise as to when it occurs: we have tons of data as to where they will and won't occur, and at what height to expect floodwaters. Even on floodplain properties there are methods to combat disasters: levees, raised platforms, stilts, etc.
As many hundred-year floodplains are turning into ten-year floodplains thanks to climate change, investing in anti-flood improvements where possible (and relocating the entire operation where not) just seems like an inevitable move. We're seeing this in the home insurance market: highly disaster-prone locations can't be insured anymore, making them financial liabilities rather than assets. The biggest favor the government can do the farms (and taxpayers) is to encourage and subsidize anti-disaster improvements, while phasing out payouts to farms that stay in high-risk conditions.