It was dropped because it was politically impossible and it wasn't worth burning political capital on it. Even just the public option wasn't able to gain traction; single payer was never going to happen in 2009.
I would just note that "...it was politically impossible" and "the Democrats were never serious in saying they wanted it" are two ways to frame the same reality. Both are true. Take your pick.
I'm not saying any democrats at the time were willing to go all in on it, but the two statements would only be two ways to frame the same reality if democrats had the ability to make unilateral decisions in the senate. They never did.
The nuclear option - changing the rules to allow majority votes to override a filibuster - has existed in potentia for a long time. The republicans have used it lately for things they consider crucial to their agenda. If the democrats wanted single payer and considered it crucial to their agenda, they could have done that. Of course neither of those "ifs" are true and we can use the lack of action to judge this.
> If the democrats wanted single payer and considered it crucial to their agenda, they could have done that.
And then watched it get blown away by next congress as soon as the GOP gained 51 seats to do whatever they want. Blowing away the fillibuster is an awful, terrible, no good idea and there is almost no legislative agenda which would validate it.
And to be clear, the GOP senators were and still are slimey bastards for basically everything they did leading up to Gorsuch. It should have never been done. They will almost certainly regret it as soon as they lose the senate.
As I recall, the rough idea was to adopt a Republican plan (RomneyCare) in order to achieve bipartisan support (and "stake holder" support). And then it became the evil spawn of the Democrats...
And that is counting Lieberman as a D; a person who backed McCain for president and who later personally killed the public option.
I do think we will get to the public option at some point. It just makes too much sense not to and would strengthen the healthcare as a whole while allowing people more choice.
Public option is unlikely to happen in the near future. Too many people start frothing at the mouth and yelling "socialism!" every time it is proposed.