They lack any other moves. I have mentioned Political Capital before, but what is it? Simply put, it's the 'currency' of politics.
Let us take a theoretical example:
Senator Alpha wants to have a bridge built in his state. He claims this bridge will greatly increase the efficiency of trade both with other states and a neighboring country. But, he is one Senator. He needs to convince other senators of this move. He starts with his own party, convincing them of the idea and providing ideas on how it might benefit the party as a whole. In order to grease the wheels, he notes that funds could be given to a construction firm in a neighboring state, which gets that state's senators on board.
That right there is Political Capital. The ability to grease the wheels, make a case, and 'fund' it through social interaction.
Now let's take it a bit bigger. A president is elected and gains a Mandate, effectively a voice from the American People in support of whatever he ran on. This Mandate is a more centralized and codified form of Political Capital, think of it as a big loan to be used to pay off the Executive's will, with the payments back being the gain of the American people.
The problem is that Political Capital is always ticking down. There is no way to passively generate it. You either gain it with your election or through kickbacks and pork-barrel spending meant to create Favors. Favors in a political context being less "I'll do this for you, then you do this for me" and more "I'll do some general kickbacks and pork, and I can call that in at a later date". It's less direct than a favor in a normal person context and acts as a lump sum payment of Political Capital with specific groups.
So, why am I explaining all this about Political Capital, Mandates, and Favors? Well, keep in mind Political Capital is -always ticking down-. It must be generated in lump sums. The Biden Admisnitrations's problem is that all the Political Capital it ever had was spent. The Capital gained from Favors was spent to make people look away from the election tomfoolery and to do the initial sweep of changes and fortifications. The plan from there then was to use the Capital gained from the Mandate in order to generate more Capital. But that fell through. The election bill and filibuster changes both died and were Capital expenses without any gain. The audits have proven a consistent drain on capital with no gain even possible. Areas the mandate could be leveraged at proved deeply unpopular. And the schismatic nature of the Admin's handlers led to easy generators like student debt relief dying too. The end result is that all the Capital ran dry, they have 0 dollars in the bank. So that only leaves the last thing they have Capital in from the mandate. Covid. And well... the problem with that bundle of bombs is that the lack of favor Capital means getting Red States onboard diplomatically is off the table.
You can't just ignore it then try to pretend the rest of it is bad. You obviously see the big issue I explicitly mention in the post and why it's a risky maneuver. Also, you seem to miss the word 'force' in that. As in, apply leverage and not just ask politely. No shit it would be bad for Red States to go along, that's why I specifically said they need to FORCE them to go along.