To understand the show prior to attending, I read the lyrics while listening to the album repeatedly. I also read all the annotations Dave Malloy wrote about his script. (The opening song said to "study up a little bit," so I did!) Malloy wrote that in W&P, Pierre is about 45, but he cast him older. Dust & Ashes is about him nearing the end of his life having accomplished nothing but drinking and reading. "Is this how I die? Sick with booze."
Age is relative. Drinking heavily could make anyone older than their time. That isn't really the point for me.
Groban was a force in the show. His presence pulled in $1mil /week with a significant drop in his absence. That speaks loudly. News reports question if Oak can do the same. I attended Groban's final performance. To use a racing analogy, Groban is the all-time Secretariat to the also rans who followed him in the Triple Crown quest...good but not great.
Again, I'm sure Oak is fine, but he just doesn't have the vocal range of Groban, and I'm sure Oak would be the first to admit that. They are two different vocal styles much like opera's Renee Fleming to pop's Cyndi Lauper.
I'm glad I got to see Groban 4 times, once on a stage table with him singing Dush & Ashes within 2 ft of me. It was thrilling. I intend to see Malloy & Oak. I would've preferred Danny Burstein, who played the lead Tevya, in Fiddler on the Roof. Danny has the pipes, the look, and doesn't need the "fat suit" that Groban said he wore to plump up. Actually, Oak doesn't need the suit either.
As the NY Times article said, the producers are "making a bet" that Oak's Ham connection will work comparing it to Phillipa Soo for Amalie. That didn't keep the show alive for more than 2 months.
If nothing else, at least I can cherish the Secretariat Triple Crown performance of Groban.