In theory he could.
However he also has the reality of how does he fund an election without the support of his party MPs?
He could appoint pro-Johnson candidates, but there is the question of just how many would he need to appoint and whether Tory party grassroots would support this too.
Theres the physical issue of running an election without your manpower from the Tory Party.
So in practice he knows that this really isn't viable as a strategy. He's run election campaigns before. He needs enough people to manage to do this.
As it stands with Cabinet Ministers apparently telling him its time, he hasn't got this. If he tried to do it he'd spark either a constitutional crisis or a party crisis.
Ultimately Trump couldn't do it without the backing on his party. Thats probably more true of Johnson.
Game Up if rumours about the Cabinet revolt really are true and I very much suspect they are.