Bitcoin never had 70%+ as far as I can remember, not for years anyway, if it has peaked over 70% back in peak times I do not remember something like that but to be perfectly honest there was a reason back than. Bitcoin cash was coming out for the first time in 2017 summer and because of that everyone moved their money to bitcoin from altcoins so they could have free bitcoin cash in return of keeping their coins on their wallets.

Considering that reason is as solid as any there was a reason why bitcoin had high dominance, that didn't resulted with bitcoin getting higher in price, it resulted with people going back to altcoins once again when the deal was done, only after couple of months bitcoin price started to go up. Hence I think they were not related.