The Conservative party was in disarray. Boris Johnson was hiding from journalists in fridges, lying in every other sentence, dodging interviews, and stealing phones to avoid difficult questions. To say the Conservative Party was on sound footing for the 2019 general election is grossly overstating the strengths of the Conservative Party.
The Conservative Party also didn’t perform particularly well at the ballot box. Despite earning an 80-seat majority, it was only able to increase its share of the vote by 1%. Labour’s, on the other hand, fell by 8%. 
This clearly suggests that the Labour party’s failings were the main factor behind their election loss, not the Conservative party’s relative strength.