Look at the whole picture and stop acting like a protestant yourself. Mass, rosary, encouraging protestants to venerate Our Lady more, having their marriage validated in a Catholic Church. These are recent occurrences leading up to his death and were moving in what direction? Tell me, where was his 'free will' taking him? Endangering his life by refusing Isra eli money, bribes, and threats. Willing to face the truth and speak out. There is clearly grace at work there. And while I am not claiming he is in heaven, we can be hopeful - because of these exterior markers - that he is not damned; that spiritually he had united himself to the one, true Church. And therefore, in charity, we should pray for his soul. If you don't want to, that's up to you, but at least accord him and his family the respect they deserve in their time of suffering.
The "whole picture" is that Charlie Kirk died without abjuring his Protestant heresies and publicly converting to the true Faith. The exterior markers here that matter are whether or not those things happened, and they didn't. Membership in the Catholic Church is public. I can point to someone I know who is Catholic and say "they are a member of the Church". I can point to someone I know who is not Catholic and say "they are not a member of the Church".
When Charlie Kirk, a public figure, an Evangelical Protestant who held heretical views regarding the papacy, the sacraments, the Blessed Virgin, etc. was sitting in a chair at his event in Utah, moments before death, we could point to him and say "he is not a member of the Church", because he wasn't. Between that moment and several seconds later, when he was dead, there were no "exterior markers" to tell us that he suddenly became a member of the Church. You are pulling that out of thin air. One moment he was speaking about gun violence, a political matter, the next he was unconscious from massive blood loss, and then dead. There are zero exterior markers that he miraculously joined the Church through "desire" in those few seconds between him being a non-Catholic heretic debating politics and him being dead. Zero. Rather than blather on about his "martyrdom" and salvation, you should consider this a sobering example that our lives are Gods to take, and He takes them when He sees fit. I do not know why Kirk died when he did, without entering the Church, but that is God's decision. Kirk was given sufficient grace and time.
The fruit of your religious indifferentism (EENS denial) is non-Catholics believing they can be saved without formally entering into the Church and receiving the sacraments. That's not what happens, however. They end up being damned. You, and every other liberal, "charitable", "Catholic" will have to answer before God as to why you denied His Dogma and contributed to the damnation of souls. You should do so serious reading and praying about this matter