@Omega_Variant @CharlesSynyard @synapsid @MeBigbrain
The ideal has always been One Man One Woman since the creation:

"A man shall leave his father and mother and cleave to his Wife (singular)..."
Gen 2:24

To say the Bible doesn't condemn polygyny is just plain wrong, we see in Deuteronomy 17:17:
"17 Neither shall he multiply wives to himself, that his heart turn not away: neither shall he greatly multiply to himself silver and gold."

Despite this being a warning from God himself to kings/rulers, we see the disastrous effects of Polygyny in the common man (Elkanah) not just in kings (Solomon being the prime example). We know that disobedience to God is a sin and of itself

Now the question is, did God have more tolerance over it? Sure? His reasons for it may have been as you stated, since in them real olden days women really had no shot to get by on their own. God has shown such "tolerance" before with, not surprisingly, another topic related to marriage: Divorce
We see the following in Matthew 19:
"6Wherefore they are no more twain, but one flesh. What therefore God hath joined together, let not man put asunder. 7They say unto him, Why did Moses then command to give a writing of divorcement, and to put her away? 8He saith unto them, Moses because of the hardness of your hearts suffered you to put away your wives: but from the beginning it was not so."

Not only do we see Jesus Christ's affirmation that marriage was always supposed to be 1 Man 1 Woman, but deviations were either tolerated (despite being in error and sinful for divorce and polygyny), or downright forbidden and worth of Death (homos, fornication, adultery)