Big executive power has been Bill Barr's raison d'etre for the past 40-odd years. The unitary executive is one of the core beliefs of the Federalist Society. Limiting executive power is about as bleeding-heart liberal a position as you can take - I think you're confusing "liberals" with "democrats" when "democrats" count as anyone who cheers against the Republicans. I also think that you're forgetting Occupy Wall Street - a much more vituperative, popular and powerful movement that came about for the exact same reason as the Tea Party. OWS's problem was they didn't organize for shit, they didn't align themselves with anything and they didn't accomplish a fucking thing. That, more than anything, is the most frustrating aspect of American liberalism: the utter inability to focus beyond our own noses. "Black lives matter" yeah but if you want to actually change anything you need more than lawn rainbows you need the Black Panthers. If the assorted amoebas of BLM and Antifa were to take one look at the 3 percenters or the Proud Boys? Fuckin' watch out. In general? Right wing rabble-rousers are a bunch of pussies. But in general? Left-wing rabble-rousers are a bunch of feckless, inconsequential pussies. It drives me crazy.
Conservative love for the unitary executive is part of the problem. I don't know the financial side of this all that well, but on the national security side congress just doesn't have much bandwidth anymore for serious detail oriented work that isn't extremely pressing. This is especially true on the republican side where a huge number of representatives entered congress with a MAGA mindset. Good national security legislation is innately bipartisan. It's not a love for the unitary executive as much as owning libs on Twitter and other performative ritualistic politics is how you get ahead and hard work doesn't count for shit. We are going to see an interesting test of Congress ability to do more than be shit flinging monkeys with the AUMF repeals the Senate is sending over. If they get repealed it would be a bipartisan step towards Congress clawing back a little shred of power, hopefully that might become habit forming but I should probably be careful what I wish for.
Federalist anything is a big part of the problem; their basic goal is to roll back the government to before the Missouri Compromise. I would argue the original shit-flinging Monkey was Newt Gingrich with his "Contract with America". The current crop has certainly devolved further but the original "fuck your governance we have feelings" posse was Gingrich and crew.