That’s not exactly accurate, Lilmod.
Reishis Chochma Yiras Hashem…. is supposed to come first.
I forget who I’m quoting (R’ Y. Salanter??)
Yirah without Ahava is a chisaron
Ahava without yirah is “gornisht”
But it is true that true Yiras Shamayim should take a logical path of leading to Ahavas Hashem.
Perhaps one way to explain this (this may not be exact), is imagine a strong, powerful, influential, kind and caring Boss. You recognize that he can fire you at any point… Yirah. But the way he interacts with you/cares for you is so, so positive, that you just want to make him happy. You know he is the Boss, but you love him, and are doing your work for him for that reason.
On the other hand, if you just do your work because you love him, when it comes to times that he does things that you don’t understand, the love may not carry you through. And you may act like a disgruntled employee.