No one wants to say he is too inexperienced and he should try to get elected to Indiana State Senate or Governor. Try again in 8 years.
I that it is his plan get known so that he is the leader of the pack in 2024 when Bernie & Biden are really too old.
My thoughts as well. This candidacy will give him an introduction to the national scene and nice campaign warchest to pursue statewide office.
After that, he can decide whether another presidential run is appropriate, or perhaps a run for US Senate first.