The OP's analysis is stupid, but I'll run with it.
The percentage for the quasi-incumbent has to be measured against the quality of his opposition. By that standard, he did fine.
Vivaswami was a pipedream, so his votes are a toss-off. Haley is a Democrat, and most of her votes were probably Democrats who changed their party affiliation for this primary because their Tuesday night CPUSA meeting was cancelled.
DeSantis, on the other hand is the ideal candidate. He is young, good looking, has the right credentials, great success as a Governor, and the proper position on every single issue. He is Donald Trump without the baggage.
And the important thing for Republicans is, DeSantis is Plan B. Nobody else. Plan B comes into effect if Trump is taken out by one or more of the phony prosecutions that are figuratively biting at his heels from now until November (and probably beyond). It is important to keep him at the top of the non-Trump heap and it is important for him not to drop out because Plan B could be Plan A in a moment's notice.