For ECB and CA these amounts are peanuts tbh.
For other boards its beneficial. NZC is also gets a big check from the BCCI cause lots of Kiwis are part of the IPL. SLCB also earned fair amount of money in last season as there were lots of SL players in the every IPL squads, guess more than 10 SL players, even net bowlers.
Not sure about CA, and even for ECB. Cricket Australia is in a much weaker position when compared to ECB, and their annual revenues are much lower. If my calculation is correct, they receive around $3 million per year from the IPL, which is a significant amount. For the ECB, such amount may be small, but not "insignificant". In case of NZC and SLCB, I agree. A number of Kiwi pacers are now regulars with various IPL sides, so are the spinners from Sri Lanka. For these two boards (along with WICB and CSA), there is a lot of dependence on funds from the IPL.
If the decision of distributing the money evenly between all boards is taken, it is going to hurt the earnings of the big 4 and that's why it's obvious why they did not agree with this decision. I really hope that the ICC will stop being a pussy. ICC should have authority over all cricket boards. The cricket boards will have to listen to ICC in this matter but it feels like that is never the case. This could have been a wise decision taken by the ICC even though it does feel like it could have been a bit unjust for the teams in the big four. But that would have been the most sensible decision overall.