Are you suggesting he isn't actually popular or rather than you do not listen to France Culture or yet something else?
I'm a bit confused as it's quite easy to check that he is indeed famous (again, not claiming it has any consequence on this work) in France related to popularizing science. I would bet, but feel free to ask around, that most people interested in scientific popularization know of him, but please do ask around, I'd be curious if it's just in my social circles.
And I don't watch TV so it won't help either.
After posting my first comment I actually did asked, first at work and later to friends/family ; the only positive answer was from someone who listen to France Inter daily. Otherwise they said they never heard of the guy.
Actually it's an interesting topic because it's far from the first time that I see some journalist talking about "someone famous", and yet I never heard of them.
It seems that there's actually no real "mainstream medias" like it used to be when I grew up, where the vast majority of people were watching the 20h everyday. Talking to adults in their 20s is quite illuminating. Things we could consider "mainstream" are unknown to them. They don't even know they exists.
FIP is cool, I even have a shortcut to play/pause it from anywhere on my system using 'mpv https://stream.radiofrance.fr/fip/fip.m3u8 --no-resume-playback'