NASCAR is on six networks this year. Fox, FS1, Prime, TNT, NBC, and USA. And I think Max has additional coverage for the TNT races.
Now, they're all in blocks so it's not like one week is NBC, one Fox, and TNT the next, and they've been doing at least two partners for a long time, but splintering it that much, including a streaming-only block with Prime doesn't seem great. Meanwhile Indy is on Fox every single race. And even NASCAR's lower series is always on CW.
The problem with streaming is that while you can really lock-in the diehards like the no blackout Apple deal with MLS, it's also going to create a barrier of entry for casuals. There's not really channel flipping on streaming, but on the other hand, with more and more dropping cable I don't know how much longer sports can bring in casuals either. There are a few reports basically saying sports are the only thing keeping people with cable. I'm one of them.