[Campion]

In a prohibition which will severely affect diocesan priests offering the Latin Mass, the Congregation expressly forbade any offering of the Latin Mass on days when the priest also celebrates the Novus Ordo

That's not exactly what it said. What it said is that a priest cannot binate (say two Masses in one day) on a day when he would normally not be permitted to (e.g., a weekday) in order to say mass in both the 1970 and 1962 Missal. It does not prohibit a priest from saying an NO Mass and a TLM on Sundays or major holidays, when bination is normally permitted.

[ebb tide]

Why couldn’t a priest offer two public Masses on a weekday?

I see that all the time.