why did old (like 90s/2000s) GPS take up to 15 minutes to get a lock, in giant bulky units, but my running watch gets it in 15 seconds?

Question

why did old (like 90s/2000s) GPS take up to 15 minutes to get a lock, in giant bulky units, but my running watch gets it in 15 seconds?

In: 3751

Answer 1

I thought this reddit stood for explain to me like I’m 5, yet reading most comments they’re waaaay beyond that.
I like simple answers, the rest I can Google if I’m interested in the technicals