only EELV has its head screwed on right here
Is there a natural reason for splitting Gard?
Yes, there's a very important geographic divide in the department between the mountains of the Cévennes (more or less lining the border with Lozère) on the one hand and the urban centre of Nîmes and the Vallée du Rhône/Petite Camargue. There are major economic, agricultural, cultural, historical, social and political differences between these regions; certainly the Vallée du Rhône - particularly places like Villeneuve-lès-Avignon - is much closer in economic/social/cultural/political terms to similar regions in PACA while the broader region outside the Cévennes has a broader 'Mediterranean' orientation leaning towards Provence.
EELV justifies its proposal by the dialect boundary between languedocien and provençal which more or less reflects the Cévennes vs. the rest boundary (although from what I can see, it would leave the Cévennol mining basin and Alès in 'greater PACA' which kind of contradicts their map, although they may have a point, given that the western half it gives to Languedoc+ is turned towards Montpellier in real terms more than the region around Alès). I don't think it's a pressing issue or egregious injustice (unlike the continued Pétainiste division of BZH), but it's an interesting proposal.
So, this is all happening to appease the EU? What other countries will be doing this?
Where on earth are you getting this idea from / what on earth are you talking about? This is all Flanby and co's making, under the false pretense of 'increasing regional competitiveness' and 'saving costs' and the inevitable bid of every French government in the past decades to destroy or vandalize regional government, so that regions become nothing more than central planning regions imposing diktat. I suggest you read
one of my rants on this topic.