The Electoral College certainly does help to create a winner take all approach to presidential campaigns in each state of the Union. This is because the winner of the voting in each state takes all of that state's votes.
The main reason why this matters is that candidates tend to take the attitude that only states whose results are in question are important. If a candidate is sure that he (or eventually she) will win a state, he will not bother to campaign there. There will be no benefit to going to such a state because winning more than a plurality of the vote is not valuable. If the candidate knows he will win the state by, for example, 52% to 48%, there will be no point in campaigning there in an attempt to get to 55%.
In this way, the Electoral College does promote a winner take all approach to presidential campaigns.