How does fundraising effect the show?

So, I tuned into Car Talk last week and it came on at the normal time, but it was inter spliced with fund raising segments. But here’s the thing: they ran it for 90 mins, but instead of tape delaying the new show, they just played some of the favorite callers with Tom and Ray jumping in to drum up support for giving.

I’m pretty new to listening on a regular basis, so I’m not sure how that works. Do local NPR stations hold fund raising on different weeks? How can they have both a new show and a clip show playing simultaneously on different stations if that’s the case. If it’s not the case, why was there a new show online?