Just got saved from a ticket – but why?

Long story short.

Stopped going 22mph over

As I’m on the side of the road fiddling with registration and insurance, guy blows by honking horn (estimated 30mph over but i’d have no way to tell)

Cop gives me stuff back tells me to slow down, chases down and pulls over guy that blew by

I pass them and think wow, they really saved me but why?

Few miles ahead at a light they are in the left turning lane and i’m in the right lane. They turn left at one of the lights (a mile or two from where my house is) but blow the horn and wave as if to let me know they knew what they were doing.

Should I be concerned?
Has this ever happened to anyone?
Were they just being good guys/ knew the cop and felt like saving me?