Since ASICs are built for mining one specific algorithm and no other, ASIC miners are invested in the survival of "their" mining algorithm.

If there are several competing coins using the same algorithm, it may be possible to incentivize ASIC miners to destroy one of them if it benefits the others, but even then it's risky.

CPUs in contrast can be used for a million different things, CPU miners are not incentivized to support any given crypto project. It's also much easier to rent large amounts of CPUs than of ASICs.