It's unlikely that the players can work well together yet, so that must be a factor. However, as fans we tend to assume that all new signings will succeed but that doesn't always happen, particularly when a large number of signings are made.
Spurs, after selling Bale, spent unwisely, going through £110m in buying seven players and have only Eriksen left, though Nacer Chadl was a decent player I always thought. Liverpool, in their £117m splurge on Balotelli, Lambert and six others, have only Can, Lovren and Lalana who play regularly, and they seem to want to get rid of Lovren. Last year, after winning the title, Leicester spent £60m on six signings, including Slimani, all of whom, according to the Telegraph, were made available for transfer this year. Three have gone already.