Based on this and I think
@LithiaWx knows this,
it was the exact opposite of what you're claiming (Shokin was NOT investigating when he should have been):
"But sources ranging from former Obama administration officials to an anti-corruption advocate in Ukraine say the official, Viktor Shokin, was ousted for the opposite reason Trump and his allies claim."
"It wasn't because Shokin was investigating a natural gas company tied to Biden's son; it was because Shokin wasn't pursuing corruption among the country's politicians, according to a Ukrainian official and four former American officials who specialized in Ukraine and Europe."
"Shokin's inaction prompted international calls for his ouster and ultimately
resulted in his removal by Ukraine's parliament."
"Without pressure from Joe Biden, European diplomats, the International Monetary Fund and other international organizations, Shokin would not have been fired, said Daria Kaleniuk, co-founder and executive director of the Anti Corruption Action Centre in Kiev."
"'Civil society organizations in Ukraine were pressing for his resignation,' Kaleniuk said, 'but no one would have cared if there had not been voices from outside this country calling on him to go.'"
Trump has claimed Biden forced out Ukraine's top prosecutor in order to benefit his son. Former diplomats say the prosecutor wasn't doing his job.
www.usatoday.com