It wasn't really that prior Administrations (GOP and Democratic) were turning a blind eye - they were just enforcing up to the limits of the resources that Congress was appropriating for that purpose.

A nit: It turns out there was always plenty of funding for securing the border, as we've seen. This is correct on the deportation part of it.

A Thune "small unassuming bill" on just border and energy could have been passed in early March, while the BBB might linger on deep into the summer.

Unlikely.

The only reason we're getting One Big Beautiful Bill - and the reason why the GOP went this way - was to put the democrats in the position they've put the Republicans in many times: either vote for cloture and pass a budget framework or shut the government down. So Schumer took the obvious way forward and voted for cloture.

There's no universe where a 'clean' bill that increases ICE and opens up things like energy exploration goes to the Senate by itself and gets 7-9 democrat votes. Won't ever happen.

The democrats are going to give Trump nothing the next 4 years; they'll only vote 'yes' on something if backed into it.