1 Fierce Competition
The primary reason for its failure initially was tough competition as, at that time, there were various strong titles like Fallout 4 that was released on the Xbox. There were various other such titles because of which there were low sales of the rise of the tomb raider.
2 Exclusivity to Microsoft
When this game was released it was exclusively released to Microsoft's Xbox. Hence, loads of people say that if it were released on all the platforms, then it would have got more sales.
3 Meagre initial sales
When the game was released, it sold just 60K copies which is considered as a failure as per Square Enix.
4 Bad timing
It is believed by the experts that because the game was released in a bad timing which is why it sold a less number of copies initially.
5 Bad sales compared to the previous game
Thelastrelease of the game in 2013 sold 186,000 in just the initial week of release. The sales of this game were three times less than the previous one that is why this one was considered as a big failure. (See Why did the Nintendo Virtual Boy fail?)
6 People decided to buy Fallout 4 first
It was also seen that people preferred Fallout 4 first rather than going for the rise of the tomb raider. They opted for this game when they had money left after buy Fallout 4; this is why its sales increased later.
7 People had higher expectations
Developers and gamers both had high expectations with its sale as they thought it would get the same market as the previous one. But, when the sale was so less in the initial weeks, it was considered as a failure. (See Why Super Mario Run is bad?)
8 It was a timed exclusive
Xbox took the rise of the tomb raider as a timed exclusive. It was first released on Xbox 360 and Xbox one on 10th November 2015; later it was released on PlayStation on 11th October.
9 PlayStation users didn’t play it
Another primary reason for its failure was that it was not released on PlayStation 4 until 11 months passed which led to decreased sales as PlayStation users didn't play it. As, when they released it, a lot of new games already came, and they forgot about this game.
10 Xbox players prefer shooter games
Xbox players love playing shooter games as compared to adventure and puzzle games such as the rise of the tomb raider. This was also one of the reasons why its sale dropped in the beginning when it was released.