It has always been the case that it is much easier for us Brazilians to understand Spanish than the other way around. Some claim that it is because Spanish is a bastardized version of Portuguese, but I have no idea how much truth is there on that claim.
Not much truth to that claim. Both evolved from the vulgar Latin. One could "maybe" make that claim about Gallego, but definitely not Castellano. Both
https://es.wikipedia.org/wiki/Historia_del_idioma_portugu%C3%A9s (See the section: El despertar de la lengua portuguesa).
https://es.wikipedia.org/wiki/Idioma_espa%C3%B1ol#Historia