Two major reasons are:
- Small Arms scandal in which a middle-man's email was leaked, he was talking about FN targeting SFF for future small arms sales.
- Diplomatic failures of the previous govt. and Belgians + Germans for HK/FN small arms.
Also all the Steyr AUG-A1s, FN Scar-L/Hs with SF and SFTS are from the trial lot which was procured among many other small arms for evaluation before Tar-21 was ultimately selected.
SFF got it FN and HKs through 3rd party(my assumption) as Belgians and Germans had cleared told no to any sale of small arms to SFF.
NSG got its share directly from the OEM as atlast they agreed to sell their weapons to a Federal CI-CT force and not the military.