I think you've misinterpreted. I believe he gave Stek a 2-year deal in 2018 because he wanted him as his back-up, which is fair, he was 35 at the time which isn't exactly past it for a keeper and wasn't a liability when called upon. Then in 2019 - as you said yourself - "bringing in international keeper who's been a number 1 keeper pretty much all his career (and all at the top level)" when he was available on a free was a smart move and one he thought wasn't worth missing out on. Brands was then left with Stek with one-year left who he could try sell but in the end he couldn't and he'll just leave this year.
When Joao Virginia was coming back in my eyes he thought "right, 4 keepers. First choice, one we can't sell, a young lad who needs his confidence rebuilding and a back-up on £38k per week" so that's why Lossl went off out on loan to shave money off the wage bill.
Maybe I'm looking too deeply into it but in my eyes it's all very straightforward and calculated.