It's widely known that Philippines' President Rodrigo Duerte is has taken a hard stance in the war against drugs. It's likely that concerns about invasive drug tests, extra-judicial killings and human rights violations led Valve to take this decision in the best interests of the players.
This is a massive blow for Dota fans in the Philippines as well as for the organisers of the tournament - Fallout Gaming and Purpose Win. The official announcement went on to state that tournament itself may still proceed but without any involvement from Valve or the Dota Pro Circuit. Whether or not the qualified teams would still consider it to be worth their time to travel for the event is up for debate however given that Valve is now exploring a possibility of running a 'replacement Major' with the same qualified and invited teams means that the incentive to participate is reduced drastically. Add to this the fact that the overall prize pool for the event will now drop from $1 million to $500,000 owing to Valve rescinding it's name (and therefore its contribution to the prize money), and you've got yourself a tournament that's on the verge of being cancelled.
Can't say this was the ideal way to start 2018 but hey, que sera sera!
Read Valve's official blog post about the Galaxy Battles Major here