You're right that there are tipping points, but they don't come at will, they come when the culture is ready for them. Push too soon, and as you note, you may actually undo progress that had already been truly won.
Culture behaves like a non-Newtonian fluid: manipulate it gently and it flows smoothly. Apply too much stress too fast, and it turns into a solid and resists you. Trump did not invent that resistance, he simply untapped it and rode it to power. The progressive movement created the resistance by applying too much pressure to a culture that wasn't ready.
And, your claim argues against itself. The problem is that minds can be changed in either direction, and the people who "didn't believe in any of it" had been precondtioned to reach that position of non-support before DEI was even a thing.
Likewise, Trump was able to manipulate people based on age-old tactics or, as you put it, he "untapped" existing resistance. So how, exactly, do progressives convince these same people?
You're suggesting they do so by not moving too fast? That they wait for the "culture to be ready for change"?
If we waited for the culture to be ready, then schools in the South would still be segregated. Instead, they were integrated under the protection of men holding rifles.
Of course the status quo doesn't change without pressure. That's why it's the status quo. There is no amount of progressive pace calibration that would have addressed this. If there was, then 400 years should have been enough time.
Again, the problem is not with progressive pacing. The problem is on the other side.
Why not 4000 years or 40000 years?
Or never? There are simply no preordained guarantees.