If they’ve been forced they might not have the option to divorce, might have been threatened by parents etc. Someone in that situation I wouldn’t blame for having an affair, tbh I prob wouldn’t consider the marriage valid in the first place..
Mutah is for Shias and haram for us, but misyar is kinda similar and is allowed:
'According to a Shī‘as, Mut’ah is permitted, but Misyar is considered to be prohibited by Shias, though it is not forbidden in Sunni’s. The similarity between Mut’ah and Misyar is that both of them are the kinds of Nikah and both require all the conditions applicable to Nikah. Nonetheless, in Misyar the couple voluntarily give up some of their rights, e.g., living together. Mut’ah, unlike ordinary Nikah, has a fixed date of expiry.
Every Nikah in Sunnis whether ordinary or not requires two adult male witnesses, whereas in Shī‘as witnesses are not required in Nikah. Shī‘a divorce requires two witnesses, whereas Sunni divorce can be executed by mere pronouncement of the words.’
Source: Misyar marriage - Wikipedia
Rightly or wrongly, a lot of ppl liken it to prostitution.. I know of quite a few Arab men who’ve come over to London and used these marriages as a means to having legalised ‘fun’ with no regards as to what might happen if the girl gets pregnant..