Box Office Bomb: Barely avoided. Combined production and marketing costs and problems during production (the "A team" from Crystal Dynamics was busy making Underworld, so production team had to hire an outside contractor for help) ended up close to the revenue generated by selling 1.3 million copies of the game, the lowest number in entire franchise.
There is a speculation within the fandom the financial failure of the entire game is the main reason why no 20th anniversary project was conducted for 2016. Other points out how Square Enix simply shapes entirely new IP using the title, focusing on creating entirely new playerbase ever since the 2nd reboot took place.
Executive Meddling: Zig-Zagged. Devs from Core Design were working on 10-year anniversary project mostly in their spare time, but after getting enough material to actually present it, they've went to Eidos to strike a deal for publishing. Eidos not only send them away with nothing, but seized all the material and handled it to Crystal Dynamics to start working on the game anyway. Thing is - while it didn't sit well with fandom and was generally a dick move, Eidos had every right to do so, as the legal owner of the franchise defending their own property.
The whole project on Eidos side was calculated as an easy cash-grab to capitalise on the series once again. It backfired spectacularly.
Toby Gard, the mastermind behind original game, was again hired by Crystal Dynamics as a consultant to help them, but limited his influence to bare minimum and voice-over for extra content. He later openly admitted he took the job only because he needed the money. He also went quite vocal how while working with Crystal Dynamics is enjoyable (he was part of the creative team of all their initial games and later won few awards for his script for Underworld), but the sole concept of remakes simply doesn't appeal to him at all and he would rather not talk about it at all.
Troubled Production: The project was initially started by Core Design. After loosing a competitive bid with Crystal Dynamics (which wasn't originally even interested in making the game at all) and being almost sued for copyright infringement, all their assets have been passed to Crystal Dynamics. Since folks there were busy making Tomb Raider: Underworld, which their own executives somehow missed, they ended up hiring Buzz Monkey Software, a company which previously helped them port Legend to PSP. Even with combined effort of both companies it was still impossible to deliver on time and the game was released almost a year overdue. Which normally wouldn't be that big deal, but in the process it completely missed the whole 10th anniversary.
What Could Have Been: The whole concept for the project and initial stages of it were done by Core Design, in their pitch to either get back to the franchise or at least deliver remaster of the first game. From all the leaked material, the game looks like a genuine remaster, simply applying modern technology to the original, but keeping Core's trademark complexity of levels and not touching the plot or characters that much. This is in stark contrast with Broad Strokes approach of Crystal Dynamics, with all of the game's content rebuilt and re-imagined from the ground up, making a lot of changes that didn't sit well with fans of the original, tying the story with their overarching narrative and, which alienated fandom the most, greatly shortening and simplifying all the Marathon Levels.