Bioware is basically following the publisher mandate. In March of this year, EA declared that they were going to cut roughly 6% of their workforce (~800 layoffs) to lower costs, likely because they (like many tech companies) over-hired during the pandemic and need to correct the burn rate to appease their shareholders. These 50 devs being cut are Bioware's unfortunate sacrifice to the layoff declaration. As to whom and why, I suspect it is a combination of things.
Bioware probably had some kind of incubation team working on a secret new project that wasn't a sequel to an existing current franchise. I know that they would often have one or two such teams going at any given time - Anthem was one such project, as was the short-lived Shadow Realms project. New projects like that are much riskier than franchise sequels, so it is likely that the publisher decided that the risk moving forward was too high and they cancelled the experimental projects in favor of focusing on their established brands (Mass Effect and Dragon Age).
It is also likely that some of the long-term veterans are quite expensive to keep - they have high salaries and have been around long enough to collect on many of the big benefits EA offers, like sabbatical leave and the like. There's also the real possibility that there could be some bad blood or major creative differences between the current studio leadership and some of those veterans that were let go.
My heart goes out to those affected and I really do hope they land on their feet. The unfortunate truth of the matter is that employers never deserve any more loyalty than they're willing to give their employees. The employer will never choose an employee over its own survival, so we as workers should expect to do the same for ourselves. I never consider long tenure at an employer to be worth much when it comes to the business decisions, because I know how little it is worth when all is said and done. Business gonna business.
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