The Republican party has a long history of just grabbing someone largely at random

Go on...

Herschel Walker was a big name NFL player popular with Texas Boomer White Men

How... random

What matters to Republicans is that they vote for Republicans. Who is or is not a Republican is a top-down decision. For people who view elections as superbowls, "name recognition" is most of it and for people who vote Republican, "Republican with name recognition" is 100% of it. This has been true since Eisenhower.

The difficulty the Republicans currently face is the top-down definition of "Republican" is increasingly toxic - it runs contrary to get-out-the-vote operations and tends to suppress the vote of all but the most partisan. A party that literally ran 2020 on "whatever Trump says" does not have a deep bench of qualified legislators eager to kiss the ring. Thus, Herschel Walker, who was still within 4 points. 4 points in a deeply-gerrymandered, formerly crimson-red state, yes... but that, again, speaks to the toxic trap the Republicans have gotten themselves into.

The best quote of this election cycle was that Republicans have a choice between embracing reason and losing in the primaries or embracing MAGA and losing in the general.