I have found within every testimony, if one were to parse them, there is always a phrase such as this. If God prepared your heart, then your positive response to God was because God prepared your heart. God initiated it. You responded.
As for the rest of mankind, He calls but there is no evidence that He prepared their hearts.
Faithful is He that calleth you for He will also do it. ... Many are called but few are chosen. ... Of the many called, why so few chosen? ... Because so few will let Him do it. [Thanks to Maj. Ian Thomas for that syllogism which I heard for the first time decades ago at Shades Mountain Independent Church in Birmingham, AL]
....”As for the rest of mankind, He calls but there is no evidence that He prepared their hearts”.....
Perhaps they simply said no....so you wouldn’t find evidence.