If you pull that chart to its full timeline, over 200TWh of coal production existed, and it's essentially all gone now, but there isn't 200TWh of gas and biomass, in total they're maybe 140TWh. There is 60 TWh of wind power production.
Now, in terms of capacity for instantaneous power, the Combined Cycle Gas Turbine plants probably do add up to similar capacity to older coal plants which were phased out, at least very close, but it's pretty rare for all that generation to actually be needed - this chart doesn't really show that.
As to "transition" the countries which look "slower" on this chart are mostly using a lot of hydro, which is very different from wind or solar, as well as being readily available from the mid-20th century a point where solar and wind power were not really established options. So we're not talking about China having a bunch of wind turbines, then kicking back for a decade and only adding more recently, but instead their enormous country has hydro power, and now it also is adding wind turbines. The UK is a small island (and some other even smaller islands which are useful for wind but don't produce hydro power) and doesn't have vast majestic water bodies like Lake Mead, so hydro power has always been a tiny niche here, and that's all you're really looking at.