Session team lacked funding to continue, their new coin sales didn't go well enough to fund operations.
I personally have criticisms of their approach outside of the official reasons. They could have used their existing DNS system to have rotating keys (PFS) by rotating the name to a new account. The lead Session dev told our team in an interview that they didn't want to do this because it forced sale of the name to have the security. But without a product, you have no funding.
