How on earth have they both managed to cause such destruction without facing any consequences?

No child related consequences. No divorce consequences except her paying the £2k in legal fees/solicitor, and as she has plenty of money, that is no skin off her back. Still living in her nice house, with her nice car and nice job which won't change. She faces no consequence from her adulterous friends, and doesn't seem to care about her family.

Scott free. Absolutely scott free and blissfully happy and in love with OW. No reality to come and bite for either of them.

Reality is that which, if you don't believe in it, doesn't go away.