Because he is in a brand new job and is probably quite optimistic and massively arrogant. Nothing has happened, nothing has gone wrong at this point. Who knows, maybe they were the 2 that he wanted out of all the defenders he could have had.
Nothing had gone wrong in the summer before his 3rd season at Chelsea the first time around too, they'd just won back to back titles in fact but that didn't stop all the reports coming out that he wasn't happy with Abramovic signing Sheva & to a lesser extent Ballack at the expense of players he wanted. I don't believe for one moment that Mourinho wasn't onboard with the Bailly signing and given how Castles regularly does Mourinho's dirty work for him in the press, considering how your first season under Mourinho went, had Mourinho not wanted Lindelof then Castles would have let us all know but we'll never know for certain anyway.
That's totally ignoring the fact that actually working with a player is completely different from watching him play external to the club (one of the many factors why transfers aren't perfect)
PL experience as a player is massive, as a manger its a factor but not major (there's the old " does he know how to prepare a team for a wet mid-week night in Stoke" which comes into managerial experience a little bit, the players gaining PL experience is more a factor I value more highly)
Klopp has still replaced players he bought, yet everyone is expecting JM to get it right first time and every time. That's never going to happen even SAF seemingly got more wrong than right in the last few years before he retired.
Matip has also come in, is he really anything other than a barely adequate stand-in? He may not have cost anything but he still got a huge contract on Klopp's say so.
Obviously it's an advantage to work with a player day to day but lets not try to pretend that Mourinho rocked up in July without a clue about Utd, the squad they had and of course the league. And I'd love to know why you think Premier League experience is so vital to a player but not a manager - I'd actually suggest it was more important for a manager as they're the one that ultimately sets up the side to play a particular way, makes decisions on resting/rotating players and of course signs the players (how suitable a player is to the PL etc). From a Liverpool perspective, I think both Benitez and Klopp took their time to adjust to the League - iinm Benitez says in his book that in his 2nd summer he looked to bring in more physical players as this was something we lacked, clearly underestimated when he first took over.
Re replacing signings, you've not quite understood the point. If Bailly/Lindelof weren't Mourinho's choices or they were signed because Mourinho didn't have the funds to sign better players as well as Pogba/Lukaku - why sign them at all then? Because Mourinho will sign anybody, for any amount of money if it improves his options for today, regardless of any long-term consequences. And if they were his first choice targets, along with Mikhi, Sanchez and possibly a few others too, then he's spent incredibly poorly. Why would you continue to back somebody that's either happy to spend £30m+ on a player that he doesn't want and or has such a patchy record in the transfer market?
He is the polar opposite of Klopp in regards to transfers. Unless we've been desperately short of options and needed somebody just to bolster the squad then Klopp has refused to settle for the next best thing. He's shown that when he couldn't get VVD or Keita (and others previously), he won't blow £30m on Johnny Evans or any other midfielder, even though it meant being slightly short for a period of time. He went without and got the player he wanted later. You say he's still replaced players he's bought but both Klavan and Karius were bought for rock bottom prices because we were short in both areas (since Klopp's first summer we've always had 2 if not 3 senior keepers at the club). They were all we could afford/were all we were willing to commit on players Klopp didn't desperately want - we didn't spend significant sums on them, expecting them to be the long term solution. Obviously in Karius's case the hope was he would become the long term answer but he was a calculated gamble for £4-5m in the hope that he'd become first choice and when his deal becomes permanent, we'd have made a profit on him. Touch wood it continues but everytime Klopp's spent a significant amount on a player they've been successful.
So you've got one manager that will sign anybody (he openly admitted he gave Woodward 4-5 names for 1 position) and or has a poor record in the transfer market, with multiple £30m+ players flopping and you've got another who won't just spend for the sake of it and his unsuccessful signings have totaled less than £10m and will be sold on for a profit. Surely you can see why a board wouldn't trust the former as much as they would the latter when it came to signing players in the future?
