West Ham have been in Europe three years running - one of only four English clubs currently in that bracket. This transfer window is about maintaining and building on that, and WHU may have approaching £250m to spend this summer bearing in mind how much is being raised in sales. It isn't about relegation.
Maguire is seen by many West Ham supporters as a short/medium term option at best; one who has been overpaid, may have questionable motivation and someone whose confidence and reputation has been shredded after the repeated criticism and lampooning. Other longer term or more cost effective options are perceived to exist, but Moyes wants some experienced, homegrown players who are deemed to be captain material. We are also talking with Ward-Prowse.
West Ham have to bolster the homegrown contingent. It's why McTominay is also of significant interest. Harvey Barnes was lined up only for an internal recruitment reorganisation to scupper it.