The Feds force employers to provide healthcare for employees. Employers are typically not in the business of providing healthcare for employees. They exist to make or service widgets. Providing health insurance was done on a voluntary basis until ACA. The problem is that government regulations have forced employers to do the government's work in many ways, which reduces freedoms and creates undue burdens on employers making them, and the economy, inefficient (ACA, tax collector, excessive OSHA requirements, unnecessary permits that exist only to raise government revenues, penalties for hiring illegal aliens that the government has incentivized to come to the U.S., purveyor of identity politics via inefficient minority quotas and hiring requirements, etc.). These regulations reduce transactions and make us all poorer.
Not only have the Feds required employers to provide health insurance, they have mandated what product they must buy. As you stated, they have to buy plans that cover existing conditions, but they cannot determine if those existing conditions are present before hiring an employee. That decreases their "margins" and makes them inefficient. That is not health insurance.
Anytime a government entity mandates or regulates, it means that the free market had previously decided such regulation or mandate was not in their interests, and/or that the issue would eventually be corrected via competition in the marketplace. Some regulations are based on values accepted by the vast majority of citizens, such as criminal penalties for murder, and some regulations are based on values accepted by a slim majority, such as the ACA. The regulations enacted by a slim majority create the most problems. If the ACA were worth a damn, the government would not have outright lied about it to the American people before enactment, and it would have passed on a bipartisan vote.
Bottom line, who are you to even think you know what a company's margins are and what they should be?