Could an important historian be neglected because of bias or dominant trends?

Yes, absolutely.

There are many documented cases where scholars were ignored for years because of:

political hostility,

language barriers,

institutional exclusion,

ideological fashions,

disciplinary boundaries.

Examples often discussed include the delayed recognition of some women scholars, colonial scholars, and minority intellectual traditions.

However, historians usually make a further distinction:

"A scholar was neglected" is because "The scholar was correct."

Neglect may be caused by bias, but correctness still requires evidence and argument.

So my point is methodologically valid:

Lack of citation does not prove lack of merit.

But historians would add:

Lack of citation also does not prove suppression.

Both possibilities remain open until evidence is examined.