You are right the previous administration made a deal with the Taliban. The Taliban deal was part of their strategy to lower the US footprint in the region as much as possible and as orderly as possible. It was done in multiple parts in coordination with the Abraham Accords to ratchet down tension in the region. Israel of course is arguably central to all the problems in the region.
The BA overturned many of Trumps policies or deals immediately after taking office, others later on. If they found the deal with the Taliban did not fit their strategy, they could have amended or cancelled it as Trump did with Obama's 2015 Iran nuclear deal. The BA did not do that. Why not? Another interesting question.
What is important to the situation now is what Putin thinks. He doesn't care about the Trump agreement. He would care about analyzing the performance of the US military under Biden's Pentagon and how the withdrawal was executed. That has nothing to do with Trump. Putin would have also sent under cover Spetsnaz to question former US trained Aftgan military staff on the latest US tactics and instructional manuals.
As for what equipment we left behind, all it takes is only one Blackhawk or A29 to get the information they need.
I would imagine the US left more than one behind. The following gives more details which I can't believe because it is staggering. I too am waiting for more information from the DoD on the real numbers and whether they were properly disabled.
The Biden Administration is hiding previously published audit reports quantifying U.S.-funded military gear into Afghanistan. Reports disappeared from federal websites over the weekend.
www.forbes.com
The relevant conclusions Putin reached are revealing themselves in real time.