What was the reasoning behind this change? Isn’t R&D something we’d encourage to be a tax write off since it reduces the cost of well.. R&D? Or is R&D not as important as I’m thinking?

It was done to try and make the bill somewhat pencil out and make the national debt increase less egregious. Everyone just assumed it would be delayed forever or reversed before it could take effect, but those negotiations failed, triggering massive waves of layoffs.

https://blog.pragmaticengineer.com/section-174/

The story that I’ve heard (probably on here) is that the administration did it to make the tax bill look more balanced over the long term by phasing out that tax write-off, while giving them (or the next administration) time to reverse it before it really impacted anything. But, nobody reversed it, until this year.

That administration really didn't like tech