if they increase price pool to 2 million, it won't do anything anyway. No one is tuning in just because the price pool is larger.
Just look at league of legends, small price pool and still way more popular than Dota in viewership.
Only reason they are 'forced' to have such a big price pool compared to all other Riot event is because the FPS players are used to inflated CSGO pricepool where some event that run every other week has a price pool of 250k+