The failure lies in the ownership model: a telco company trying to build a walled garden. Other walled gardens failed as well of course including some that were basically much more competitive in terms of networking. E.g. AOL failed a few years later because the world outside their walled garden was more interesting. It never really stood a chance of surviving despite being much more similar to the internet at that time.

Operators trying to build walled gardens is a pattern that repeated itself until it became such a low margin business that the only operators able to make a profit were those merely offering full internet over 3G and 4G and not even bothering with the black hole of R&D needed to keep up with what was happening elsewhere. There were attempts in both standards to grandfather in a lot of stuff that is now exclusively done over IP but none of it ended up being popular. The history of mobile phone operators is just a long succession of attempts to copy things from the internet at the time and trying to turn them into walled garden things. Each of those things failed. We're not watching TV via operator provided services. We're not doing video calls via operator provided services, their game portals have long died and faded away. We're not browsing any WAP sites. Instagram wiped out what little adoption MMS ever had. None of it stood a chance.

The incentives and ownership were just wrong and the role as operators as essential middlemen just never panned out in the real world as they hoped.

Many telcos of course managed to convert themselves into successful mobile operators ultimately but their role was diminished to providing network access. My android phone has a phone stack. The only stuff that comes in via my phone number is basically recruiter cold calls. It's a small internet device with some quaint legacy features that I rarely use. Really, numeric identifiers that you have to punch in? In 2020? How is that still a thing? I remember memorizing shit like that a few decades ago.

So, minitel is merely an early and probably expensive incarnation of that. France telecom subsidized the devices and had to earn it back via regular network charges. I doubt that generated anywhere near what they hoped in revenue.