I had the same questions. Apparently discovery of the prior conviction is what lead to them being fired:
> When the company discovered Sohaib Akhter’s felony conviction, it terminated both brothers’ employment during an online remote meeting on Feb. 18, 2025
from https://www.justice.gov/opa/pr/federal-jury-convicts-virgina... which is a better source on this.
That prompts the question of why background checks are so lax that they were hired before this was discovered.
The company involved here is apparently based in Washington, DC, which has a "Ban the Box" ordinance that limits employment background checks for most kinds of jobs. And apparently DC's version of the law is particularly strict.