Giving away electoral votes

The bill in California to give all the State's electoral votes to the winner of the national popular vote even if that candidate lost the popular vote in California has now passed both houses and gone to the Governor for his signature. I posted about this before and wondered why the Democrats would do this in a State that's usually pretty safely in the Democratic column. It's a give-away to Republicans unless enough red states with a counter-vailing number of electoral votes adopt the rule. I just don't get it. I particularly don't get it when it's clear that this move is only coming from Democrats. That means that the states most likely to adopt it are going to be those whose home-state votes would tend to go for Democratic candidates. It's as though one side in a war decided to unilaterally dis-arm.