Not done for political reasons.
Are you suggesting they did this for technical or economic reasons? Like what? Is the US charging an unreasonable storage fee? I'd read the article, but the site seems to be down.
1. The bars were of an old variety and therefore not standard tradable.
2. Transporting them, refining them, and recasting exceed the cost of selling kind #1 and obtaining kind #2
Here's one such link though it appears there's some primary source everyone is rewriting: https://www.rfi.fr/en/france/20260404-french-central-bank-ne...
It appears that the gain mentioned is a realization of their asset value. I would also speculate that what happened is that they wanted LBMA bars because those are a standard variety and therefore easily tradable. An arbitrary LBMA bar is generally fungible. I would also speculate that they held many bars in the US from ancient times. After 2008, they repatriated 200-ish tonnes and 'upgraded' them (which I would speculate again is 'ensured they were LBMA-standard').
https://www.moneymetals.com/news/2024/10/05/why-france-repat...
These articles all have the flavour of the game of telephone common in this style of article where the currency that the gain is in changes wording, the motivation seems to shift, and phrasing lacks real detail instead relying on 'upgrading' and 'refining'.
I wish there were a good LLM agent that were capable of tracing all this back to the real original source that spawned all these things, but the information environment is currently full of smoke and getting real news is quite hard.
I can't realistically conclude whether this was politically motivated or not. The original motivation is sufficiently strong on its own, but it is completely normal for governments to move something to be earlier, or to do a marginal thing if there is other gain.