if they are so good why was gmail completely compromised without their knowledge
They now claim its secure again because they are encrypting internal traffic. It's such a high priority and centralized target with so much valuable intelligence that any such claims have to be taken with a grain of salt.
MUSCULAR was the the one where the NSA tapped Google's inter-datacenter fiber lines in order to spy on their internal traffic.
https://www.washingtonpost.com/world/national-security/nsa-i...
Which is still really bad but not the same as these software vulnerabilities.