We've been over this before, too.
Someone like Sergio is very young and had no children with Liz. To my knowledge, Sergio has not cashed in on her life insurance policy, and he has a child with his new wife. If ever a time to reach for more money, a child would certainly be a catalyst. I read an interview before that said him and his new wife bonded over loss, as she had lost her sister:
Who killed Elizabeth Barraza? Case of Tomball woman shot while setting up garage sale remains unsolved 5 years later.
Some people love being married, and Sergio may be one of them. We don't know what their dynamic was like, but maybe he loved having a wife to come home to every night. We don't know much else past that so the rest is speculative. Not saying that Sergio is, but many men marry solely for the purpose of having someone to do their cooking, cleaning, and laundry.
On the flipside, someone like Brandon Bevers getting married again would have looked highly suspicious for some time. He had teen girls with his wife and lost her in a very sudden manner. Wreckless spending and a quick new wife would have been a very, very bad look for him.
One more example is my great Uncle Dee. He must be in his 90s by now, but his wife passed from natural causes when he was in his 70s or so. About a week later he married a woman that looked EXACTLY like her.