There are many reasons why they had to let Clive go as I explain in my book which you can get here
bit.ly/3wuKMJ5. The reasons were explained to me by a person who worked closely with the band between 1980-1990, Keith Wilfort and Adrian Smith. And can be summarized as follows:
Clive was having personal problems (family and girl friend) since the beginning of '82. While the band was in the UK, things were kind of sorted because the proximity of his relatives, friends and girl friend but as soon as the band went outside of the UK, things started to get complicated. The band was obviously getting bigger by the minute and with fame, as both Adrian and Bruce comment on their book, access to drugs and booze become much easier. Now, imagine young Clive having to sort his personal problems, being famous and having access to drugs and booze and really no one to rely upon because you're the young and handsome drummer of a now World famous Heavy Metal band, what do you do? Overindulge... He was given four opportunites to sort himself up (all well explained in the book), the last being after the Beast On The Road tour on December 10, but ALAS two things happen during the last weeks of December. First, the relationship with his girlfriend ends in a bad way and secondly, and more important, Clive's dad dies. This is all too much for Clive and the band (Steve) has no other option but to let Clive go because there was no chance at all they can give him more time to sort himself up before they had to go to Jersey to start work on Album No. 4.