I don't think Trump (or anyone, really) would have had much impact on China's internal politics during that period, and opening up is very much an internal matter. It's generally hard at this point to see external pressures (small as they are) having much impact at all.

I don't deny that Trump has potentially enabled Xi to make some moves faster and bolder. But those moves would likely have happened anyway and on the bright side it's maybe easier for the world to see what's going with the lies being so obvious nowadays.

Xi Jinping's actions are only minorly influenced by Trump. China are on a 100 year strategy. Trump's Presidency is a tactical curiosity at best.