He explains their pivot with Ben to GOP in this podcast episode.

The main argument was that democrats policies were detrimental to their business.

https://www.youtube.com/watch?v=n_sNclEgQZQ&t=11s

Mr. Andreessen has been involved with high level politics for a long time. This is not "random radicalization". I will not comment on the quality of the politics but it feels fairly deliberate.