If you don't have a large enough LEO constellation you will have sporadic and predictable coverage. This is especially true if you want global coverage to monitor a military like the USA with a global presence.
2. These gaps would be measured in minutes, and are zero when you considered the combined coverage of all none-nato countries. Anything that we don't want seen is done under cover.
1. Some reports say that they've only been detected recently; referencing multiple undetected occurrences during the Trump presidency; o they've been working for X years already. If they're undetected, they can view into gaps referenced above. If this program has been going on for 5-10 years undetected then it still could have been of value to China/Russia/Whoever owns them.