Timing Chain broke after engine rebuild?

A few days ago, my timing chain broke on my car listed above. The car has been kept in excellent health (scheduled oil changes, tune ups, repairs, etc.). In 2022, my mechanic replaced the head gaskets, PCV valve and lifter assemblies. I'm wondering if when they were doing this rebuild, could they have not made correct adjustments to the timing chain? Should the timing chain have been inspected when they did the rebuild in 2022? I spent $6k on the rebuild in 2022, and now they are telling me I need to replace the entire engine, and they are quoting me the full price (about $10k). I feel like I'm not being treated properly.