You can, but some will say it's not very good style. " as two examples of how to rewrite it.
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Bbk_agpI wonder if it's possible to start a sentence with "that"Yes. It's not that uncommon; however, when the that-clause is very long, as in your case, and sometimes even when it's short, it's customary to replace the whole clause with "it" and then move the clause to the end, as Grammar Geek has suggested above.