I’m aware he became a Montanist. However, I’ve also read that he never split from the Catholic Church and died Catholic.
Yes and we can be sure that he was not alone in this views. If we assume that the Catholic position is correct and the church has always baptized infants from the very beginning, Tertullian indicates that at least by the era of his writing (he lived c. 160-c. 225) there were people disagreeing with this. Another way to look at it is that infant baptism was on among many trends that was gaining increasing dominance in the church and Tertullian is not happy about it.
I don’t, and never claimed to, agree with everything Tertullian said. I just used an important early Christian writer to point out that the following statement made by you was open to debate: “In the early Church, there was no controversy about whether infants should be baptized.”