Complex sentence: This was the only router supporting a separate USB modem, and was the only router compatible with BT's new USB ADSL service, which made it very popular and firmly established DrayTek as a key player in the broadband Internet hardware market in the UK.
Split into simpler sentences: This was the only router supporting a separate USB modem, and was the only router compatible with BT's new USB ADSL service. These factors made it very popular and firmly established DrayTek as a key player in the broadband Internet hardware market in the UK.