It's a fact. A free and fair referendum cannot be held by an occupying force, because their very presence biases the results.
This is true even if the occupiers are honorable. It goes double for a leader like Putin, who imprisons and assassinates his political opponents.
> U.S. invades other countries whenever it likes. > > Why can't Russia do just the same?
In both cases it's wrong. But if you want the realpolitik answer, it's because the US has a competent military.
> If Ukraine feels so lucky as to fight a Goliath - let Zelensky be that David and send as many soldiers to death as he please until the unrest inside his country ends his presidency or the other side's forceful actions lead to the same result. Harsh, but kinda fair. Know your fights. Don't fight with a Goliath alone, if you are a tiny David, and if you are - group up with others and bow to them if the success of your very existence becomes dependent on their help.
David won against Goliath, remember? That's the whole point of the parable. At least find a metaphor that supports your argument.
Besides, isn't finding support exactly what Zelensky's been doing all this time? The US may be withdrawing its support, but European support is increasing. And in terms of population, economy, and military spending, Europe is a lot bigger than Russia.
You say Ukraine should know their fights, but doesn't that apply more to Russia? They expected the war to be over in 3 days, and it's been 3 years. Putin vastly overestimated the strength of his own army, and underestimated the resistance Ukraine would put up.
How much longer can Russia's reserves actually last? Those steadily rising Russian interest rates indicate an economy that's edging ever closer to collapse.