Susan Collins was the only holdout who stood for the principles of the affordable care act, believing that Republicans should work with Democrats to make a better health care system. Others like Lisa Murkowski and Shelly Moore Capito might have felt the same way, but were sucked in by Mitch's last minute inclusion of funding for opioid substance abuse to keep the bill alive.
Mitch only needed 51 votes. He had the VP on call, but in the end it didn't matter when Lee and Moran dropped their support. There was no way he was going to get this "Better Care Reconciliation Act" through Congress, and it seems like he knew it. Some are arguing that Mitch went through the act just to show those incalcitrant members of Congress and Trump himself that it simply wasn't possible. Eventually, Republicans will have to work with Democrats if they want to get some of their provisions into the health care act.
More likely, the White House will now seek to undermine the Affordable Care Act, as they are currently doing the Environmental Protection Agency. From their point of view, this should have been the game plan all along. But, I guess they thought the fear of getting "Trumped" in the primaries would keep GOP members in line, and they could claim a huge victory in crushing the Obama administration's landmark health care bill.
Also, they hoped to roll back Medicaid expansion, using the money to help fund the massive tax cuts they are proposing. Medicaid is primarily administered through the states so the White House has little control over it. Both a blessing and a curse, much of our health care is state controlled, so you have some states with excellent health care coverage and others with horrendous coverage. The ACA hoped to equalize this to some degree with Medicaid expansion, so that families living in poorly covered states would have a safety net, knowing these states were unlikely to accept the health insurance exchanges. Even still, many states refused to accept Medicaid expansion.
Why is anyone's guess? You have ardent Libertarians like Paul Rand who don't believe the government should be offering any kind of subsidies to Americans. For them, it is pay as you go or fall by the wayside. They seem just fine with the idea that 10 per cent of the country remains uninsured, but their form of free market capitalism would leave many many more uninsured in the future, as they also want to go after Medicare and Social Security.
The irony is that the US already pays more per capita for public health care than virtually any other country in the world, yet still has a large number of uninsured and underinsured citizens. The problem isn't money but management, which is why the American Medical Association and American Hospital Association would like to see a single payer system like most European countries have. However, private insurance companies exercise tremendous influence over health care policy in this country and as a result we see a deeply fractious system that sees many persons falling through the cracks, even with the ACA.
One would like to think that Republicans may now finally realize they have to work with Democrats, but that is highly unlikely. They have a constituency, which they have been telling for 7 years how evil the ACA is, even employing "death panels" to determine who would get health care. Conservative politicians worked up so much resentment and anger among the GOP base that anything short of total repeal would be seen as defeat. So, I really don't know how Mitch McConnell worms his way out of this one.
You can bet Trump will be pinning all the blame on Mitch, as he is not one to accept any blame himself. Sadly, much of Trump's base will stand behind him, as they have throughout all his failures in his first 6 months in office. That shining moment in the Rose Garden now seems so long ago.