It has always been made clear that phone records indicate he did not leave the village in which he was staying.
If you believe that Esther meant "I can see you" literally (both times?), you presumably believe that:
* Dan rented/borrowed/bought/stole a car from someone who has never come forward
* Dan managed to sneak across France under lockdown, then back again
*
While this was happening, Dan left his phone with a friend in the village
* The friend repeatedly whatsapped Esther from the village
* The friend also had a video call with Esther on the afternoon of her disappearance
In other words, yep, it's completely batshit insane.
The French police were, at the time, trying to push the theory that Esther had chosen to voluntarily disappear. The French police are notorious for ALWAYS pushing this theory - the right to disappear - in missing person cases. Look up the work of the ARPD if you want to know more.
Note that at the same time, the SPANISH police said that they believed she'd had an accident. But that wasn't nearly as exciting for the armchair detectives, was it?
Note also that the French police, post-body discovery, now agree with their Spanish counterparts.
Finally, note that even when the French police were trying to push the voluntary disappearance angle, they repeatedly reiterated that Dan wasn't a suspect.
Because he was hundreds of kilometres away.
BTW, you want red flags? Let me reiterate:
Esther travelled to Spain to go hiking alone
![Triangular flag :triangular_flag_on_post: 🚩](https://cdn.jsdelivr.net/gh/joypixels/emoji-assets@5.0/png/64/1f6a9.png)
in winter
![Triangular flag :triangular_flag_on_post: 🚩](https://cdn.jsdelivr.net/gh/joypixels/emoji-assets@5.0/png/64/1f6a9.png)
in high mountains.
![Triangular flag :triangular_flag_on_post: 🚩](https://cdn.jsdelivr.net/gh/joypixels/emoji-assets@5.0/png/64/1f6a9.png)
She did not speak Spanish.
![Triangular flag :triangular_flag_on_post: 🚩](https://cdn.jsdelivr.net/gh/joypixels/emoji-assets@5.0/png/64/1f6a9.png)
She wore dark colours,
![Triangular flag :triangular_flag_on_post: 🚩](https://cdn.jsdelivr.net/gh/joypixels/emoji-assets@5.0/png/64/1f6a9.png)
yoga pants,
![Triangular flag :triangular_flag_on_post: 🚩](https://cdn.jsdelivr.net/gh/joypixels/emoji-assets@5.0/png/64/1f6a9.png)
and inadequate, wornout footwear.
![Triangular flag :triangular_flag_on_post: 🚩](https://cdn.jsdelivr.net/gh/joypixels/emoji-assets@5.0/png/64/1f6a9.png)
She did not carry any form of GPS other than her phone.
![Triangular flag :triangular_flag_on_post: 🚩](https://cdn.jsdelivr.net/gh/joypixels/emoji-assets@5.0/png/64/1f6a9.png)
Her route was not set in stone.
![Triangular flag :triangular_flag_on_post: 🚩](https://cdn.jsdelivr.net/gh/joypixels/emoji-assets@5.0/png/64/1f6a9.png)
She did not know if her intended destination had a winter room.
![Triangular flag :triangular_flag_on_post: 🚩](https://cdn.jsdelivr.net/gh/joypixels/emoji-assets@5.0/png/64/1f6a9.png)
She was known to carry inadequate provisions.
![Triangular flag :triangular_flag_on_post: 🚩](https://cdn.jsdelivr.net/gh/joypixels/emoji-assets@5.0/png/64/1f6a9.png)
She was known to follow bad bivouac practice.
![Triangular flag :triangular_flag_on_post: 🚩](https://cdn.jsdelivr.net/gh/joypixels/emoji-assets@5.0/png/64/1f6a9.png)
She ascended late in the day.
![Triangular flag :triangular_flag_on_post: 🚩](https://cdn.jsdelivr.net/gh/joypixels/emoji-assets@5.0/png/64/1f6a9.png)
All this took place during a global pandemic, when there were fewer people in the mountains due to national and regional restrictions.
Each one of these would either make an accident more likely, or make it harder to get help after an accident. There are reasons that hikers have best practice guidelines to follow.