It could be that when the first marriage took place incorrect information was provided. This incorrect information was discovered thereby making the marriage invalid and they married again with the correct information.
Incorrect information wouldn't necessarily invalidate the marriage - but it really depends which bit of information it is.
The change to being divorced on the second record would suggest that the groom may not have been free to marry on the first occasion, which would certainly invalidate that marriage, and be an offence of bigamy potentially.
But to be certain, you would need to look for his original marriage record and then a divorce record probably between these two marriages in 1940 and 1944, and I would also look at newspapers to see if there was a charge of bigamy against him. Not surprisingly, there was a huge spike in bigamy cases during, and just after, WW2, as there had been, although not quite so large, in WW1.
I have a similar example I use in talks I give on marriage - a couple who married during WW2, both claiming to be widowed (they weren't), but then married again 10 years later, and in front of the same registrar, by which time they both had actually obtained their divorces.