This reasoning also would justify mandatory colonoscopies, or requiring a 3 mile daily run, for 100 million people. Yes, that might reduce the load on the health care system long term (except the colonoscopy & PT departments ...), but historically in the U.S. that would have been viewed as a galactic overreach.
The crucial difference between cardiovascular diseases and severe COVID is that COVID comes in waves. In a very short period of time a large number of people can end up with the virus, thus having a significant chance to develop serious pneumonia. All at the same time, in a very short time span. While lots of people suffer from cardiovascular diseases and cancer every year, they are distributed over the year. You don't usually see thousands of people having strokes in a given area in the span of a week or two, for instance.
It's this sudden surge of people needing ventilators and ICU beds that overwhelms the healthcare system of an area, causing repercussions on those that are sick for other reasons or get injured in accidents. For instance, in Italy cancer screenings on vulnerable subjects have been postponed for months, if not a year, due to the ongoing pandemic. Who knows how many people have now a higher risk of cancer due to hospitals and clinics being overwhelmed by COVID patients.
COVID vaccines are not sterilizing, but it's getting quite clear that they somewhat reduce the circulation of the virus too by reducing the viral load of symptomatic and asymptomatic carriers. At least they greatly greatly reduce the strain on doctors and avoid disruption of society at large, which is by itself a solid choice for mandating them.
The only possible choices here are to a. neglect the virus, with potentially serious social repercussions and loss of human lives, or b. resort to containment measures, which hamper the economy and are deeply unfair towards vaccinated people which objectively risk much less from the virus, or c. mandate vaccination, which is the only choice that avoids lockdowns and (most) deaths.
Also, vaccine mandates aren't anything new. That's how rubella, diphtheria, polio, smallpox, mumps, .. have become a thing of the past. They've been put in place on for decades, and no-vax movements have always been small and irrelevant before before social media came with droves of dubious content.
The load on the system is apparently hugely different. The system has managed to accommodate people with colon cancer and heart disease, so mandating those things hasn't been as pressing from that perspective. Meanwhile, covid has filled up hospitals and ICUs
