[82lsju]

Stanford couldn’t put in a hosting bid as the stadium is being re built

That's obviously not true.
1. The NCAA has allowed bids in the past where the event was held at a different stadium than the host school's regular stadium.
2. I question the time allocated to re-configure the football stadium.  The concert is May 31.  The Regionals ended on May 18.  The SuperRegionals will end on May 25.
    Farm Aid III had 69,000+ music fans on 9/19/1987 just 6 days after a Nebraska football game.
    The Penn State stadium was transformed beginning on Tuesday for a concert on Saturday in 2017.
    This 2024 article describes transforming soccer stadiums overnight for a major pop concert.  (Converting TO a concert configuration is easy as the concert people are well prepped to do it.  It also notes that the conversion back to a sports stadium takes more time since the ground condition is a concern.)

The question I'd have of Stanford is why they said they couldn't do what others do.

a few potential factors in this case

1.  this is the first large concert in the stadium so they might want to allow some extra time as everything will be done for the first time
2.  these concerts are the first two in the Coldplay tour so they may also want a little extra time to work out the kinks in their set up and tear down processes, being the first concerts they have some flexibility on how long they plan to do the set up, their next concert is June 6 in Las Vegas and that gap is longer than the gaps between most of the venues on the tour (5 days here vs generally 3 days)   https://www.coldplay.com/tour/ 
3.  it seems to me that access is a little more restricted in the stadium compared to other venues given it is below grade and really only has the one ramp to access the field

more speculatively

4.  I don't know if they would be allowed to work overnight to do the setup and teardown, I know they did two shifts during much of the stadium construction but I don't think they did work overnight
5.  I don't know if they had to do any work in the stadium to prepare for the concerts (e.g., more power), if they did that would also complicate the schedule

[82lsju]

Stanford couldn’t put in a hosting bid as the stadium is being re built

That's obviously not true.
1. The NCAA has allowed bids in the past where the event was held at a different stadium than the host school's regular stadium.
2. I question the time allocated to re-configure the football stadium.  The concert is May 31.  The Regionals ended on May 18.  The SuperRegionals will end on May 25.
    Farm Aid III had 69,000+ music fans on 9/19/1987 just 6 days after a Nebraska football game.
    The Penn State stadium was transformed beginning on Tuesday for a concert on Saturday in 2017.
    This 2024 article describes transforming soccer stadiums overnight for a major pop concert.  (Converting TO a concert configuration is easy as the concert people are well prepped to do it.  It also notes that the conversion back to a sports stadium takes more time since the ground condition is a concern.)

The question I'd have of Stanford is why they said they couldn't do what others do.

a few potential factors in this case

1.  this is the first large concert in the stadium so they might want to allow some extra time as everything will be done for the first time
2.  these concerts are the first two in the Coldplay tour so they may also want a little extra time to work out the kinks in their set up and tear down processes, being the first concerts they have some flexibility on how long they plan to do the set up, their next concert is June 6 in Las Vegas and that gap is longer than the gaps between most of the venues on the tour (5 days here vs generally 3 days)   https://www.coldplay.com/tour/ 
3.  it seems to me that access is a little more restricted in the stadium compared to other venues given it is below grade and really only has the one ramp to access the field

more speculatively

4.  I don't know if they would be allowed to work overnight to do the setup and teardown, I know they did two shifts during much of the stadium construction but I don't think they did work overnight
5.  I don't know if they had to do any work in the stadium to prepare for the concerts (e.g., more power), if they did that would also complicate the schedule