Every italian media news outlet, starting with skysports(and Marotta himself, but then GMs aren't always telling the truth) They did not want to sell, period. They were able to convince him not to try and force a transfer, and that was that. Sure, if you offered them €100m, maybe it would've been a different story...
As for upgrades, well, how many do you know of? I mean, Marcos Alonso isn't some shite player, he's good. How many LB do you know of who are better than him? And how many of those not already playing for clubs that simply won't sell? The only high profile LB who's better than Alonso who moved this summer was Mendy -and he choose City.
LBs better than Alonso don't exactly grow on trees...