Almost everyone sided with Germans against Czechs. Czechs were demonised by international mass media as persecutores of Germans in Sudetendland same way as Serbs were deminonised as persecutoers of Albanians in Kosovo. Slovakia was pressured to separate as Montenegro today and in the end the remainded of Bohemia got occupied.
It is true that Poles took side of international community against Czechs. I am not justifying this misdeed but the motive was to take back the Zaolzie region which Czechs stole from Poles in 1919 when Poles were fighting against Bolsheviks. If not this sorry dispute, Poles probably would remain neutral or pro-Czech.