I think that is way too much to give for an older player. They would have been better off keeping the 2nd and drafting.
The texans were finally in a good position and they are going to blow it.
I would approach it from a different POV, let me share and I do think you make a decent point, however...
Nico is entering Year 4 and then he's a free agent, I like him quite a bit but he only arrived when CJS showed up, maybe the Texans don't see him in their long term plans
Maybe they see Diggs as a 2-3 year guy while CJS is on his rookie deal
And maybe they don't want to have to see Nico go and then start over with more rookie WRs, they want to try and strike right now.
There are a lot of moving pieces here and they can replace that 2nd between now and April 2025.
I wouldn't be too upset yet.