#1 The results speak for him
Beyond all the talk of aesthetics and an entertaining style of play, there is the only thing that really matters in football, which is the end result.
When results are poor, coaches are given the sack as Lopetegui found out, and when results are great, they get a stay of execution, as was the case with Zinedine Zidane last season in the Champions League.
Since Solari's appointment, Real Madrid has seen a massive upturn in fortunes, winning all four matches that he has taken charge of, scoring 15 goals and conceding just two, coming on the back of just one victory in their previous seven managed under his predecessor Julen Lopetegui, where they scored just four and conceded 13.
Results are all that matters, more so at a club like Real Madrid where winning is already ingrained in the DNA of the club, and by virtue of the winning start he has made to his managerial tenure, he should be given the job permanently.