What did Poland and the Czech Republic have in common in the 9-10th centuries?

The adoption of Christianity according to the Roman model, and not from Byzantium, like Serbia, Bulgaria and Russia. The Czechs accepted it earlier.

The alphabet became the Latin alphabet.

The state appeared later than in Western and Southern Europe. For example, in the Balkans, the first Slavic state appeared in 681, 150 years earlier than the Czech Republic and 180 years earlier than Poland. In Western Europe, the state appeared 400 years earlier on average (at the turn of the 5th and 6th centuries).

The main trade routes did not pass through these countries; they were away from the trade route “from the Varangians to the Greeks” and from the Mediterranean Sea.