MSCI World futures are traded nearly 24 hours, while the index constituents only update their prices when their local country stock markets are open - typically this means 1/3 to 2/3 of the index constituent prices are actively updating, the rest are frozen at their last close price.
The futures price can be thought of as the market’s guess at the true index level, if all the constituent markets were open.
Additionally, MSCI World futures are not very liquid so the differences can be even larger. For a single-country index with liquid futures (eg S&P 500) you will see much smaller divergences.