"extensively believed" is a correct and usable phrase in written English.
It means widely or widely accepted by a large number of people. You can use it when talking about a commonly held belief or idea, or to describe something that is widely considered to be true. Example: It is extensively believed that practicing mindfulness can improve mental health. In this sentence, "extensively believed" is used to convey that the belief about the benefits of mindfulness is widely accepted and held by many people.
The first two tests have given a confusing picture, not least because of high tyre wear, but after analysing the lap times extensively I believe some things have become established.
As Salmonella eut operon and corresponding mutants have been studied extensively, we believe similar results will be obtained for Vibrio.
Pink Floyd's EMI catalogue includes Dark Side of the Moon, Wish You Were Here and The Wall – albums that still sell extensively and are believed to bring in millions of pounds a year.
Zaihan Mohamed Yusof, a reporter for The New Paper, a daily newspaper in Singapore that has covered the match-fixing cases extensively, said he believed Mr. Tan was still in the country.
The Mediterranean diet and other traditional menus have been written about extensively, and are believed to have been carefully selected over centuries to promote good health -- but as Dr. Walter Willett points out, "people eat what they can grow, gather, kill or buy, and their choices are dictated by weather, geology, geography, economics and even politics".
Proteostasis under proteotoxic stress, while less extensively studied, is believed to share much in common as HSR.
Brazilian red propolis was found to be rich in isoflavanoids, a chemical compound that has been researched extensively and is believed to be responsible for the majority of biological properties inherent in propolis [ 8– 10].
Among different training-induced neuronal signals, activation of MAPK (mitogen-activated protein kinase) is extensively studied and widely believed to be essential and critical for LTM consolidation from invertebrates to vertebrates (Alberini and Kandel, 2015).
This results show that neural crest cells and muscle progenitor cells are more extensively mixed than previously believed during arch development.
The neurotoxic effects of methamphetamine have been extensively documented and are believed to reflect both its vasoactive effects, which can result in ischemia and necrosis as well as its cathecholaminergic effects, which can result in damage to dopamine neurons, psychosis and seizures [27], [28].
