My husbands is no longer best friends with his mate due to the friends nasty wife. Should my husband move on

My husband Bradley and his best mate Mark have been friends for 33 years. We have put up with Marks wife for the last 20 years to keep the friendship going. Marks wife is such a nasty person, who has put our whole family down behind her husbands back. She puts people down to make herself sound good. She uses people for her own gain. But both my husband and myself know that to keep their friendship going we have to keep the peace with his wife. About a year ago we stood up to her, she went crazy and has had nothing to do with us since. Quite frankly we are so glad to be rid of her, but now Mark is missing from our lives. Mark is also very sad about losing Bradley s friendship but he is taking his wife's side. Marks wife has said that she will leave Bradley if he contacts us. Mark is such a good man who is worth fighting for. We have tried all the last year to sort something out, but Marks wife will not give one inch. Do we give up or try. Good friends are hard to find. Bradley and Mark have a lot of history. Thanks for your help.

Updates
Many thanks for your advice. When it comes down to it, it is Marks choice what he chooses to do. It will be difficult for him to have a friensdship with my husband when I can never be there, when our 2 families can never get together for BBQ's, birthdays etc. It is a loss for everyone concerned except Marks wife.