LBJ, both as Senate Majority Leader and President, would get votes by awarding cooperating senators with goodies for their states. Find out what Manchin, Sinema, Finestein, and other opposing the filibuster want, and give it to them in exchange for abolishing the filibuster.
Whatever was needed (a bridge repair, rural hospital wing, water treatment plant, etc.) would be a permanent improvement and a good use of government dollars.
It's a win-win situation. Without the filibuster, the Dems could accomplish their whole agenda and save our economy and democracy.