You've said it yourself the AH-64E is the better machine and India needs to diversify its fleet, an over dependance on Russia has led to a lot of issues in the past. Russia has consistently proven unable or unwilling to provide adequate after sales support to most Russian-origin equipment in India meaning a lot of the kit is plagued by unreliability and high levels of downtime. All the purchases and investment in military gear India has made in Russia and still Russia is delaying every single project/procurement and asking for more money? This is the time to show the Russians they either perform or they will get hurt in their pocket.
US equipment on the other hand has high levels of availability written into the contract- Boeing is legally obligated to ensure the IAF's C-17 fleet maintains a 85% availability rate. These are figures one could only dream of with Russian equipment.
It is a win-win deal all around.
