Hello
"Everyone were convinced that Ryan would pitch on Saturday."
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"Everyone <u>was</u> convinced that Ryan would pitch on Saturday."
Everyone were does not make sense,
everyone was does.
This is a simple mistake of point of view. Sometimes it can get confusing, which leads to grammar mistakes.
'Were' would be used in a sentence like "Where were you guys?"
'Was' would be used in a sentence like "I was gonna go, but I didnt."
Hope this helps!
Have a great day!