Paris to Brussels, Thalys doesnt have a monopoly?

I understood that DIRECT connections between Paris and Brussels were available only on Thalys... however it appears that Eurostar also covers that route? I get this impression from the Eurostar website which offers a booking. As we would be staying in the 5th in Paris, a departure from Gare du Nord, offered by Eurostar would be a good choice for us. Any negative views and am I simply misinformed about the monopoly?