The phrase "ample evidence that many" is correct and usable in written English.
It can be used when discussing the existence of significant proof or support for a claim involving a large number of subjects or instances.
Example: "There is ample evidence that many students benefit from online learning environments."
Alternatives: "substantial proof that numerous" or "considerable evidence that a lot of".
There is ample evidence that many such referrals are business decisions, not medical ones.
We have ample evidence that many crucially important projects are now long overdue.
The Nyaya-sutras probably were composed by Gautama or Akshapada about the 2nd century bce, though there is ample evidence that many sutras were subsequently interpolated.
The bad news is that there is still ample evidence that many women are starting out their working lives on worse pay than men, partly because they are going into sectors where pay is lower overall.
But the process has been uneven, and there is ample evidence that many people are still struggling in the aftermath of one of the most vicious storms to hit the region.
They are concerned the Islamic expansion will be a success, following the same concern they had for Communism". It is still very early in the president's term, and there is ample evidence that many powerful people within the establishment are still worried by the tone and direction Mr. Ahmadinejad has taken.
Although the water columns periodically break, there is ample evidence that in many cases they can be restored.
In antiquity there is ample evidence that there were many genders exhibited, as referenced in classical writing.
Special laws shield Indian security forces from accountability for deaths in custody, despite ample evidence that there have been many hundreds of such cases.
Years before the leak, this April, of the Panama Papers — a cache of documents from Mossack Fonseca, a law firm in Panama City that specializes in the creation of anonymous shell companies — there was ample evidence that the global plutocracy has many outlets for dissimulation in the realm of personal finance.
Ron Wimmers, a retired resident of Dayton, observes that "there's ample evidence that he has migrated in many different directions".
