It's much easier to climb than to be demoted. Due to all the shielding and the huge MMR deficit you need to actually be demoted tiers theres a lot of bronze players 'stuck' in silver (and silver players 'stuck' in gold, and golds in plat, etc), so the season resets are also useful for unsticking people.
Up to gold on the other hand people even get promo helper for free wins for their promo series, so it's not that unreasonable for genuinely silver 1 or silver 2 level players to just play enough that they happen to get a lucky streak to get promoted to gold, despite not 'deserving' it.
Theres not much special for being a silver player compared to bronze, so it's not really a problem that some bronze level players get placed into silver initially. In subsequent seasons they'll be at a more appropriate level (although they've hopefully improved by then).
Also keep in mind matchmaking is all MMR based, and ranks are strictly cosmetic.