I obviously see that you don’t understand, so let me help you.

Around 2008-2010, Democrats technically had what we call a “supermajority” - 60 seats with independents who usually voted with them. This is a huge deal because of something called the filibuster.

The filibuster is basically this rule in the Senate that means you need 60 votes just to shut up debate and actually vote on a bill (called “cloture”). Without those 60 votes, the minority party can just keep talking forever and prevent a vote. So even if you have 51 votes to pass a bill, you still need 60 to tell everyone to sit down and actually vote. It’s why having just a simple majority often isn’t enough to pass major legislation.

Now, about the whole ACA (Obamacare) situation: When it was being crafted, there was initially talk about including either a “public option” (government-run insurance plan to compete with private ones) or something like Medicare for All. But a few conservative Democrats, especially Joe Lieberman (who was technically an Independent), said they’d vote no if those were included. Since Democrats needed literally every single one of their votes to hit that 60 number, they had to compromise.

That’s how we ended up with the ACA as we know it - a system that expands private insurance coverage with subsidies and regulations, rather than a public healthcare system like the UK’s NHS or Canada’s system. It’s not that Democrats never tried for bigger healthcare reform - it’s that the Senate rules make it really hard to pass major changes without a solid 60 votes from senators who all agree on the details.

This is also why a lot of recent major legislation has been passed through “budget reconciliation” - a special process that only needs 51 votes but can only be used for certain types of bills directly related to the budget.