For curiosity's sake, what exactly do you think Republicans will do to "kill the ACA"? I doubt they're going to introduce a bill that revokes the ACA in its entirety. They killed the mandate almost a decade ago and the marketplace healthcare plans have continued to limp along, depending on the state. What's next?
It’s simple. One of the original tenants of the ACA was to provide subsidies for most people earning up to what would be the upper middle class between this and the insurance mandates, it would prevent the death spiral where only the sick would sign up for it, making the cost go up until it was almost unaffordable to anyone and unprofitable for the insurance companies making them leave the exchange.
The first blow was when the Supreme Court killed the mandates. The second blow just happened when they killed the subsidies last year.
The expanded subsidies, which were a Covid-era enhancement some 10+ years after ACA was enacted.