Luminous Productions was the creator of Forspoken, and until the merger, Luminous will continue working on the game's previously announced In Tanta We Trust DLC. Final Fantasy XV was released in 2016 by Square Enix, but prior to that, Luminous' staff largely comprised just another development team within the company.
The former stated that the merger would help it create higher-quality AAA games. One of the specific reasons is that Luminous has "not only with AAA title development capabilities, but also technical expertise in areas such as game engine development."
Forspoken may have surpassed Square Enix's sales expectations, but those of Forspoken are more likely to be the result of a mix of critical and casual reactions. Forspoken is a game that both critical and casual audiences enjoy well.
A merger is always preferable to countless layoffs. Hopefully, Luminous Productions' being remerged with Square Enix will only lead to better games.