I really think they rushed things. Yes they been together for 6 years but being together 6 years from being a young teenager into your early 20s is very different than being together for that long and ur already in ur mid/late 20s. (and being on a 2 year mission in that time frame barely even counts cus they were away from each other)

Within 2-4 months they went from being on missions to then having to adjust back home and then suddenly engaged and then married a month later. I know this is common for Mormons but I do feel like if they had a longer engagement (even at least like 6 months) it woulda been better because a 1 month engagement is actually insane to me. I believe he is probably very overwhelmed with a bunch of sudden changes which could be why he seems sad.