I think a lot of what folks see as a "Louisiana influence" in Houston is mostly "Gulf Coast TX" vs the rest of Texas.
It's not that it's a Louisiana influence, it's that we're all on the gulf coast and all have a lot in common. (Not with New Orleans so much, but certainly with Lake Charles/etc.)
That somehow gets misnamed as a "Louisiana influence", when really it's just the region we're in.
As to Hurricane Katrina: We took in about 250K evacuees but only about 40K stayed permanently (which is a bunch, of course). I'd guess most of those were the sort who liked being here better, so they made lemonade out of the lemons that the storm forced upon them. [0]
[0] https://www.fastcompany.com/40460412/after-hurricane-harvey-...